Apparatus and method to improve quality of moving image displayed on liquid crystal display device

ABSTRACT

A liquid crystal display device comprises a panel having pixel electrodes arranged at intersections of a plurality of signal lines via switching elements for transmitting display data and a plurality of scanning lines for transmitting control signals, and a control circuit for controlling the panel. The liquid crystal panel is divided into first pixel regions and second pixel regions adjacent to the first pixel regions. The control circuit carries out impulse driving in which the control signals transmitted to each of the scanning lines are activated two times in one frame period for displaying an image. The control circuit writes the display data in either one of the pixel regions and writes reset data in the other pixel regions when the control signals are activated once of the two times. By writing the reset data in the pixel regions, the display data written in an immediately preceding frame are reset. In consecutive frames, the display data written in the pixel regions are always reset in one frame period. Therefore, blurring in a moving image can be alleviated. Since writing the display data and the reset data is carried out separately in the first pixel regions and in the second pixel regions, flicker is prevented from occurring in a display screen.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device ofactive matrix type and a method of controlling the liquid crystaldisplay device. Especially, the present invention relates to a techniquefor preferable image display.

2. Description of the Related Art

Liquid crystal display devices of active matrix type using TFTs (ThinFilm Transistors) as driving elements have been in wide use as displaydevices for personal computers or the like. Generally, liquid crystaldevices of this kind often adopt a display method called a TN (TwistedNematic) type. A liquid crystal display device of TN type are formedwith twisted nematic cells in which arrangement of liquid crystalmolecules are consecutively twisted by 90 degrees, with the liquidcrystal cells sandwiched between two transparent electrode-platedsubstrates. The liquid crystal display device lets light penetratethrough when a voltage is not supplied between the electrode-platedsubstrates.

FIG. 1 shows an outline of a TFT (Thin Film Transistor) driving liquidcrystal display device described above.

This device comprises TFTs and pixel electrodes 1 laid out in the formof a matrix. Gate electrodes of the TFTs which are switching elementsare connected to scanning lines G1, G2, . . . , Gn each transmitting agate signal output from a Y driver 2. Drain electrodes of the TFTs areconnected to signal lines D1, D2, . . . , Dm each transmitting a datasignal output from an X driver 3. Source electrodes of the TFTs areconnected the pixel electrodes 1. Counter electrodes facing the pixelelectrodes 1 are also laid out (not shown). Liquid crystals (not shown)are sandwiched by the pixel electrodes 1 and the counter electrodes,forming liquid crystal cells C.

Data are written in the liquid crystal cells C by sequentially causingTFTs to be on by pulse-like gate signals sequentially supplied to thescanning lines and by transmitting the data signals simultaneouslysupplied to the signal lines to the pixel electrodes 1 (line-sequentialdriving). Information of the data signals written in the liquid crystalcells C is retained until the pixel electrodes 1 are driven in asubsequent frame. This control of retaining the information in theliquid crystal cells C until next data signal writing is generallycalled hold driving.

FIG. 2 shows a waveform of a driving voltage and a response waveform ofthe liquid crystal cells C when the TFT driving liquid crystal displaydevice described above is driven in the hold driving method. Thewaveform of the pixel response corresponds to the amount of lightpenetrated through the liquid crystal cells C. A state of writing datain one of the liquid crystal cells C is shown here.

The Y driver shown in FIG. 1 drives each of the scanning lines in every16 ms, and generates an high level pulse of the gate signal. The Xdriver 3 generates the data signal in synchronization with the gatesignal. Polarity of the data signal is inverted at every frame scan andso-called frame inversion driving is carried out. Within the 16 msperiod shown in FIG. 2, all the scanning lines are scanned although thewaveforms thereof are not shown.

For example, in a period of first three frames, an absolute value of avoltage supplied between the pixel electrode 1 and the counter electrode(not shown) is 5 V in all the frames. Therefore, the liquid crystal cellC in FIG. 2 lets the light penetrate through the cell C and white isdisplayed on a screen. For the remaining three-frame period, the voltagebetween the pixel electrode 1 and the counter electrode (not shown) is 0V. Therefore, the liquid crystal cell C shuts the light and black isdisplayed on the screen.

Generally, a response time of the liquid crystal cells C in the TN typeliquid crystal display device is longer than the scanning period of oneframe. Especially, the response time of the liquid crystal cells C in ahalf tone continues for several frames, as shown by a dashed line inFIG. 2. Recently, a liquid crystal cell called a π cell having a shortresponse time has been developed.

As has been described above, the TN type liquid crystal display devicedisplays an image by being driven in the hold driving method. In holddriving, information in the liquid crystal cells C is retained until asubsequent data signal is written. As a result, blurring (image tailing)occurs in a moving image due to partial overlap of display data in aprevious frame. Such blurring does not occur on a CRT (Cathode Ray Tube)display.

FIG. 3 shows waveforms of a voltage driving a CRT according to aso-called impulse driving method. Light is emitted from a pixel only inthe case where the voltage is supplied to the driving signal and anelectron beam is emitted on the pixel. Data scanned in an immediatelypreceding frame disappears with a shift of the driving signal to lowlevel so that no blurring occurs.

In order to alleviate the blurring on the liquid crystal display device,impulse driving has been tried on the liquid crystal display device.Details of this trial have been described in Digest of SID98 pp.143–146. Liquid crystal display devices of this type uses the π cells orthe like having a short response time.

FIG. 4 shows waveforms of a driving voltage and a response waveform of aliquid crystal cell observed in the case of impulse driving of a liquidcrystal display device. As in the case shown in FIG. 2, white isdisplayed for first three frames and black is displayed in the remainingthree frames.

The liquid crystal display device scans each of the scanning lines twicein every 16 ms (one frame). A first scan is used for receiving a datasignal and a second scan is used for resetting the liquid crystal cells.In other words, impulse driving is realized by writing black data aftera predetermined time has elapsed since the data signal were written inthe liquid crystal cells C. “W” shown with arrows in FIG. 4 refers to anoperation of writing white, while “B” means an operation of writingblack. “R” refers to a resetting operation. In this manner, display datain the liquid crystal cells C are retained only for a predeterminedperiod T1 in one frame and blurring in a moving image is alleviated.

FIG. 5 shows an example of a display screen in the case where theimpulse driving described above is carried out. In FIG. 5, liquidcrystal cells in white display white and hatched cells display black.

As waveforms in FIG. 5 shows, display data (white) are written at thefirst scan in a display period (16 ms) of one frame. At the second scanin one frame period, reset data (black) are written in the liquidcrystal cells. In other words, as shown in top of FIG. 5, the displaydata and the reset data having band-like shapes move from the top to thebottom in the scanning in one frame.

However, line-sequential writing of the display data (white) and thereset data (black) in alternation causes flicker. Especially, when adisplay speed of the liquid crystal cells C is low, or when a scanningperiod (refresh rate) is long, flicker becomes large.

Japanese Patent Application Laid-open Publication No. HEI 10-62811describes a liquid crystal display device comprising a plurality of Xdrivers and Y drivers and individually driving neighboring liquidcrystal cells. This liquid crystal display device secures time to writeand reset for each of the liquid crystal cells by carrying out partiallyoverlapping write and reset operations on the cells. In this manner,contrast of display data is improved. However, liquid crystal displaydevices of this kind have the plurality of X drivers and Y drivers,which leads an increase in circuit size. Furthermore, since the numberof signal lines becomes double, a problem of aperture ratio reductionalso occurs.

In order to improve brightness of a display image, a backlight isgenerally arranged, facing a liquid crystal panel comprising pixelelectrodes, TFTs, and a control circuit thereof. However, when theimpulse driving described above is carried out, pixel electrodes havingreset data written therein and thus displaying black absorb light fromthe backlight. As a result, a problem of wasteful power consumptionoccurs. Moreover, since an image displayed by impulse driving has lowerbrightness than an image displayed by hold driving, it is necessary toincrease the brightness of the backlight. As a result, power consumptionincreases.

In the case where a plurality of fluorescent tubes laid out in parallelare used as the backlight, a problem of uneven image display caused by adifference in a degradation speed of each fluorescent tube also occurs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid crystaldisplay device and its controlling method to improve quality of movingimages. Especially, the present invention is aimed at alleviation ofblurring in image and prevention of flicker and ghosts.

Another object of the present invention is to efficiently turnbacklights on and off to reduce power consumption.

Still another object of the present invention is to provide a backlightwhich does not cause uneven image display.

According to one of the aspects of a liquid crystal display device inthe present invention, the liquid crystal display device comprises aliquid crystal panel in which a plurality of signal lines fortransmitting display data and a plurality of scanning lines fortransmitting control signals are laid out vertically and horizontally,and pixel electrodes are arranged at intersections of the signal linesand the scanning lines via switching elements, and a control circuit forcontrolling the liquid crystal panel via the signal lines and thescanning lines. The liquid crystal panel is divided into first pixelregions and second pixel regions adjacent to the first pixel regions.

The control circuit carries out impulse driving in which the controlsignals supplied to the respective scanning lines are each activated twotimes per one frame period for displaying one image. The control circuitwrites the display data in the first pixel regions and writes reset datain the second pixel regions when the control signals are activated onceof the two times. The control circuit writes the reset data in the firstpixel regions and writes the display data in the second pixel regionswhen the control signals are activated the other time of the two times.By writing the reset data in the pixel regions, the display data writtentherein immediately before are reset. In a plurality of consecutiveframes, the display data written in the pixel regions are always resetwithin one frame period. Therefore, blurring in display image can bealleviated. Since writing and resetting of the display data are carriedout separately in the first pixel regions and in the second pixelregions, flicker can be prevented from occurring on a display screen.

According to another aspect of the liquid crystal display device of thepresent invention, the display data and the reset data are sequentiallywritten in the first pixel regions and the second pixel regions dividedin the form of stripes along the scanning lines. The regions in whichthe reset data are written exist separately in a plurality of the pixelregions. Therefore, blurring in display image can be alleviated andoccurrence of flicker in the display screen can be prevented.

According to another aspect of the liquid crystal display device in thepresent invention, the first pixel regions and the second pixel regionsare divided in lattice-like form. The display data and the reset dataare sequentially written in the first pixel regions and the second pixelregions divided into lattice-like form. The regions in which the resetdata are written are separated into a plurality of the pixel regions.Therefore, blurring in display image can be alleviated and flicker canbe prevented from occurring on the display screen.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprisesbacklights facing the first pixel regions and the second pixel regions,on the backside of the liquid crystal panel. Each of the backlights isturned on in synchronization with writing display data in the firstpixel regions and in the second pixel regions, respectively. Each of thebacklights is turned off in synchronization with writing reset data inthe first pixel regions and in the second pixel regions. Therefore, acontrast ratio between when the display data is written and when thereset data is written can be increased and an easy-to-see screen can beconfigured. Furthermore, since the backlights corresponding to pixelregions in which the display data are not written are turned off, thereis less power consumption.

According to another aspect of the liquid crystal display device in thepresent invention, the backlights comprise light-emitting diodes, orfluorescent tubes, or a PDP. Therefore, the backlights can be configuredin accordance with the size of the first pixel regions and the secondpixel regions.

According to another aspect of the liquid crystal display device in thepresent invention, the backlights comprise fluorescent tubes. The cycleof one frame is adjusted in accordance with a cycle of an alternatingcurrent signal supplied to the fluorescent tubes. By writing the displaydata in accordance with a peak of brightness of the fluorescent tube,the contrast ratio between when the display data is written and when thereset data is written can be increased without on-off controlling thefluorescent tubes.

According to another aspect of the liquid crystal display device in thepresent invention, light guide plates are arranged on the backside ofthe liquid crystal panel, facing the first pixel regions and the secondpixel regions. Furthermore, the liquid crystal display device comprisesa fluorescent tube each arranged at one end of each of the light guideplates. Light emitted from the fluorescent tubes is guided to the firstand second pixel regions by the light guide plates. Therefore, thenumber of the fluorescent tubes can be minimized.

According to another aspect of the liquid crystal display device of thepresent invention, the control circuit receives the display data for twoimages per frame. The control circuit displays the data by discardingdata of pixels corresponding to the first pixel regions and the secondpixel regions for writing the reset data, of the display data.Therefore, complex data processing on display data unnecessary. It isalso unnecessary for the display data to be stored in a buffer memory orthe like. Consequently, flicker can be prevented without complicatingthe control circuit.

According another aspect of the liquid crystal display device of thepresent invention, the control circuit receives the display data for oneimage per frame. The control circuit writes a portion of the displaydata in the first pixel regions when the control signals are activatedonce of the two times, while it writes the remaining display data in thesecond pixel regions when the control signals are activated the othertime of the two times. Therefore, the received data are all used as thedisplay data without being deleted.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device has a hold drivingfunction for activating each of the control signals once in one frameperiod, and writing the display data in all the pixel electrodes. Thecontrol circuit controls switching from the hold driving to the impulsedriving and vice versa, depending on an image to be displayed. Forexample, a moving image is displayed by the impulse driving while astill image is displayed by the hold driving. In this manner, optimalscreen display for any image can be realized.

According to another aspect of the liquid crystal display device in thepresent invention, the backlights in which brightness can be adjustedare arranged on the backside of the liquid crystal panel. A variance inbrightness between the cases of hold driving and impulse driving can bereduced by increasing the brightness of the backlights compared to whenhold driving, when impulse driving.

According to another aspect of the liquid crystal display device in thepresent invention, gamma correction is carried out during the impulsedriving and the hold driving. During the impulse driving, the controlsignals are activated more times than in the hold driving. Therefore, achange in the amount of light penetrating through the liquid-crystalcells is accelerated by gamma correcting more rapidly in the impulsedriving than in the hold driving. Brightness can be increased in thismanner.

According to another aspect of the liquid crystal display device in thepresent invention, the control circuit selects the scanning linesaccording to an order the scanning lines are arranged in. Therefore, thecontrol circuit can be configured without substantially changing aconventional circuit.

According to another aspect of the liquid crystal display device in thepresent invention, the control circuit selects the scanning linesaccording to a predetermined order which is not related to the order thescanning lines are arranged in. Therefore, flicker can be prevented fromoccurring with certainty.

According to another aspect of the liquid crystal display device in thepresent invention, the first pixel regions and the second pixel regionsare divided, each including a plurality of the scanning lines. Thecontrol circuit selects the scanning lines according to the order theyare arranged in, in the first pixel regions and the second pixelregions. Therefore, without complicating the control circuit, flickercan be prevented from occurring with certainty.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of control lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the control linesvia switching elements, and a control circuit for carrying out gammacorrection in response to a temperature change of the liquid crystalpanel. Therefore, regardless of the temperature change in the liquidcrystal panel, brightness and contrast of a display screen is constant.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of control lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the control linesvia switching elements, a plurality of first backlights arranged on thebackside of the liquid crystal panel and separated from each other, anda plurality of second backlights each adjacent to the first backlightsbut separated from each other. Pseudo-impulse driving can be realized byalternately turning on and off the first backlights and the secondbacklights. In this manner, blurring in image can be alleviated andflicker can be prevented from occurring.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of control lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the control linesvia switching elements, a plurality of backlights on the backside of theliquid crystal panel adjacent along the scanning lines, and a controlcircuit for controlling the liquid crystal panel via the signal linesand the control lines. The control circuit normally drives the liquidcrystal panel without inputting a reset signal, and displays data.Furthermore, the control circuit carries out on-off control of thebacklights. In response to the backlights turned on and off, thescanning lines facing the backlights are controlled by the controlcircuit. A period of scanning the lines agrees with the scanning periodof the liquid crystal panel.

The control of the scanning lines by the control circuit is carried outas in a conventional liquid crystal display device. Therefore, acost-increasing factor does not exist. Consequently, preferable movingimage display can be realized by exchanging only the backlights.

According to another aspect of the liquid crystal display device in thepresent invention, light corresponding to the scanning lines is turnedoff immediately before the scanning lines are scanned. In this manner,maximum brightness of the liquid crystal panel can contribute to thedisplay.

According to another aspect of the liquid crystal display device in thepresent invention, backlights larger than a pixel, such as fluorescenttubes, can be used.

According to another aspect of the liquid crystal display device in thepresent invention, quality of displaying moving images can be improvedby extending the time no data is displayed.

According to another aspect of the liquid crystal display device in thepresent invention, quality of displaying moving images can be improvedfor all gradations.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of control lines for transmitting controlsignals laid out vertically and horizontally, and pixel electrodes arearranged at intersections of the signal lines and the control lines viaswitching elements, a light guide plate facing the panel, and abacklight arranged at one end of the light guide plate and supplyinglight to the light guide plate along the scanning lines. The light guideplate comprises a plurality of luminescent parts along the scanninglines. A portion of the luminescent parts emits light to the liquidcrystal panel by collecting light guided to the light guide plate. Theremaining luminescent parts do not collect light at this time. Forexample, when display data are displayed on the liquid crystal panel,the luminescent parts in which light is collected are sequentiallyswitched in accordance with control of the liquid crystal panel, whichenables impulse driving to be easily realized. Therefore, blurring inmoving image can be reduced and flicker can be prevented from occurring.Furthermore, since the light guided to the light guide plate can be usedefficiently, power consumption can be reduced. Moreover, since nofluorescent tubes are used, uneven display caused by degradation of thefluorescent tubes does not occur.

According to another aspect of the liquid crystal display device in thepresent invention, along the scanning lines in the light guide plate, aplurality of film-like scattering parts exist for totally or irregularlyreflecting light passing through the light guide plate in response tocontrol from the exterior. The luminescent parts of the light guideplate are formed by irregular reflection of the light by the scatteringparts. By controlling the scattering parts from the exterior, theluminescent parts can be formed easily at a desired position in thelight guide plate.

According to another aspect of the liquid crystal display device in thepresent invention, the scattering parts are arranged in parallel on asurface of the light guide plate. For this reason, the scattering partscan be formed easily.

According to another aspect of the liquid crystal display device in thepresent invention, each of the scattering parts is arranged on a surfaceof the light guide plate, on the side of the liquid crystal panel. Lightscattered by the scattering parts is emitted toward exterior of thelight guide plate. The light is emitted on a portion of the liquidcrystal panel facing the luminescent parts (or the scattering parts).Since the boundary between the luminescent parts adjacent to each otherbecomes clear, impulse driving can be carried out with better visibilityand flicker can be prevented.

According to another aspect of the liquid crystal display device in thepresent invention, the scattering parts are arranged on a surface of thelight guide plate, on the opposite side of the liquid crystal panel. Thelight irregularly reflected by the scattering parts is emitted on theliquid crystal panel, passing through the light guide plate. Since nolight-shutting material on the side of the liquid crystal panel, such asthe scattering parts, is arranged on the light guide plate, emissionefficiency can be improved. Furthermore, the boundary between thescattering parts adjacent to each other becomes inconspicuous.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises aplurality of light guide plates facing each other. Each of thescattering parts is arranged between the light guide plates. Bysandwiching the scattering parts between the light guide plates, thescattering parts can be protected. Furthermore, a light emission systemcomprising the scattering parts and the light guide plates can be formedeasily and precisely.

According to another aspect of the liquid crystal display device in thepresent invention, the scattering parts are arranged between the lightguide plates and on outer surfaces of the light guide plates. By formingthe scattering parts with a plurality of layers, light passing throughthe light guide plates can be scattered with certainty.

In this liquid crystal display device, the scattering parts are arrangedwithin the light guide plates, so as to cut across a direction light isguided. Light passing through the light guide plates always passesthrough the scattering parts. Therefore, the light can be scattered withcertainty.

According to another aspect of the liquid crystal display device in thepresent invention, the scattering parts are orthogonal to the directionlight is guided. Therefore, when the scattering parts are arranged so asto cut across the direction light is guided, the scattering parts andthe light guide plates can be joined with high accuracy.

According to another aspect of the liquid crystal display device in thepresent invention, the scattering parts are diagonal to the directionlight is guided. Therefore, the light scattered by the scattering partsis emitted in a large dose in a direction orthogonal to the directionlight is guided, that is, toward the liquid crystal panel.

According to another aspect of the liquid crystal display device in thepresent invention, the scattering parts are formed with a liquid crystalfilm of high-molecular type. Therefore, the scattering parts can beformed easily. Furthermore, by controlling an electric field supplied tothe scattering parts, light scattering can be controlled easily.

According to another aspect of the liquid crystal display device in thepresent invention, a resin layer covering low molecular liquid crystalsin the liquid crystal film is formed with high-molecular liquidcrystals. Therefore, in a state where the scattering parts penetrate thelight, scattering can be prevented from occurring at an interfacebetween the low molecular liquid crystal and the resin layer.

According to another aspect of the liquid crystal display device in thepresent invention, the low molecular liquid crystals and thehigh-molecular liquid crystals are aligned orthogonal to a liquidcrystal film surface in a state where voltage is not supplied thereto.This liquid crystal film scatters light when an electric field issupplied thereto.

According to another aspect of the liquid crystal display device in thepresent invention, the low molecular liquid crystals have negativedielectric anisotropy. In this liquid crystal film, liquid crystalmolecules are directed orthogonal to the electric field when theelectric field is supplied.

According to another aspect of the liquid crystal display device in thepresent invention, the low molecular liquid crystals and thehigh-molecular liquid crystals are aligned orthogonal to a directionlight is guided in a state where voltage is not supplied thereto. Thisliquid crystal film scatters light when an electric field is suppliedthereto.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the scanning linesvia switching elements. A luminescent period in which an image to bedisplayed in one frame period is output to exterior of the liquidcrystal panel can be adjusted manually. Therefore, a viewer of thedisplay image can adjust the luminescent period for the most optimalview of the display image. For example, the luminescent period islengthened when still image is viewed, while it is shortened when movingimage is viewed. Since the luminescent period is adjustable inaccordance with how the viewer of the display image feels, blurring inthe moving image can be alleviated and flicker can be prevented.

According to another aspect of the liquid crystal display device in thepresent invention, brightness of the liquid crystal panel is keptconstant in cooperation with controlling the luminescent period.Regardless of whether the display image is still or moving, thebrightness can always be kept constant, so the screen becomes easy toview.

According to another aspect of the liquid crystal display device in thepresent invention, the brightness is controlled by adjusting brightnessof a backlight facing the liquid crystal panel.

According to another aspect of the liquid crystal display device in thepresent invention, the brightness is controlled by adjusting the amountof display data signal written in the pixel electrodes.

According to another aspect of the liquid crystal display device in thepresent invention, the luminescent period is adjusted by on-offcontrolling a backlight facing the liquid crystal panel.

According to another aspect of the liquid crystal display device in thepresent invention, impulse driving is carried out, in which each of thescanning lines is scanned twice in one frame period, and display dataand reset data are written in the pixel electrodes. The luminescentperiod is adjusted in accordance with a period data is displayed.

According to another aspect of the liquid crystal display device in thepresent invention, the luminescent period is adjusted by opening andclosing a shutter facing the liquid crystal panel.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the scanning linesvia switching elements. A luminescent period in which an image to bedisplayed in one frame period is output can be adjusted in accordancewith a speed of motion of the image displayed on the panel. Therefore,blurring in moving image can be alleviated by shortening the luminescentperiod in the moving image display and flicker can be prevented.

According to another aspect of the liquid crystal display device in thepresent invention, a display image is judged to be a moving image andthe luminescent period is adjusted for the moving image, when estimatedmotion of a DC component in DCT (Discrete Cosine Transform) exceeds asize of a block comprising a predetermined pixel matrix. By using theDCT method used widely in motion compensation for moving images, imagescan be judged to be still or moving with certainty.

According to another aspect of the liquid crystal display device in thepresent invention, impulse driving is carried out, in which the scanninglines are scanned twice in one frame period, and display data and resetdata are written in the pixel electrodes. The luminescent period isadjusted in accordance with a period of displaying the display data.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the scanning linesvia switching elements. The liquid crystal display device has a holdcontrol function in which an image to be displayed is output in oneframe period and an impulse control function in which an image to bedisplayed is output in a predetermined period within one frame period.When the display image is a still image, the hold control is carried outwhile the impulse control is carried out when the display image is amoving image. Therefore, blurring in the moving image can be alleviatedand flicker can be prevented from occurring.

According to another aspect of the liquid crystal display device in thepresent invention, the hold control is switched to the impulse controlin the case where a ratio of the moving image to all of the display dataexceeds a predetermined value.

According to another aspect of the liquid crystal display device in thepresent invention, the displayed data are judged to be moving image dataand the hold control is switched to the impulse control, when thedisplayed data changes over a period of two or more frames.

According to another aspect of the liquid crystal display device in thepresent invention, the impulse control is carried out by opening andclosing a shutter facing the liquid crystal panel.

According to another aspect of the liquid crystal display device in thepresent invention, the impulse control is carried out by scanning thescanning lines twice in one frame period and writing the display dataand the reset data in the pixel electrodes.

According to another aspect of the liquid crystal display device in thepresent invention, brightness of a backlight facing the liquid crystalpanel is increased in the impulse control than in the hold control.Therefore, brightness of a moving image can be equal to brightness of astill image, and a screen becomes easier to view.

According to another aspect of the liquid crystal display device in thepresent invention, brightness of a display image output is made to bethe same between the impulse control and the hold control. Since thebrightness of display can be kept constant regardless of whether a stillimage or a moving image is being displayed, the screen becomes easier toview.

According to another aspect of the liquid crystal display device in thepresent invention, the pixel electrodes are controlled by polysiliconTFTs (Thin Film Transistors) whose switching speed is faster than aswitching speed of amorphous silicon TFTs. Therefore, blurring in movingimage can be alleviated especially at the time of the impulse control.

According to another aspect of the liquid crystal display device in thepresent invention, a display image is judged to be moving when a ratioof pixels of the display image in one frame which is different frompixels of the image displayed in an immediately preceding frame to allpixels of the displayed image exceeds a predetermined value or more, andimpulse control is then carried out.

According to another aspect of the liquid crystal display device in thepresent invention, motion compensation is carried out by using DCT. Whenan average of a DC component of the display image in one frame and anaverage of the DC component of the image displayed in an immediatelypreceding frame differs by a predetermined value or more, the displayimage is judged to be moving and impulse control is carried out.

According to another aspect of the liquid crystal display device in thepresent invention, motion compensation is carried out by using DCT. Whencompressed image information includes vector information indicatingimage motion, the image is judged to be moving and impulse control iscarried out.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel and backlights. In the liquid crystal panel, a pluralityof signal lines for transmitting display data and a plurality ofscanning lines for transmitting control signals are laid out verticallyand horizontally, and pixel electrodes exist at intersections of thesignal lines and the scanning lines via switching elements. The liquidcrystal panel comprises a plurality of control blocks divided into nportions along the scanning lines. The backlights are arranged facingeach of the blocks. The liquid crystal panel carries out hold driving inwhich each of the scanning lines is scanned once in one frame period anddisplay data are written in the pixel electrodes. The backlightscorresponding to the respective blocks are turned on for a predeterminedperiod immediately before scanning the corresponding blocks. A responsetime of each pixel in the liquid crystal panel is set smaller than:

-   -   1 frame period×(n−2)/n.        Therefore, the pixels complete responding with certainty before        the backlights are turned on. As a result, blurring in moving        image can be alleviated.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel and backlights. In the liquid crystal panel, a pluralityof signal lines for transmitting display data and a plurality ofscanning lines for transmitting control signals are laid out verticallyand horizontally, and pixel electrodes exist at intersections of thesignal lines and the scanning lines via switching elements. The liquidcrystal panel comprises a plurality of control blocks divided into nportions along the scanning lines. Each of the backlights faces each ofthe blocks. The panel carries out hold driving in which each of thescanning lines is scanned twice in one frame period and the display dataand reset data are written in the pixel electrodes. The backlightscorresponding to the blocks are turned on for a predetermined periodimmediately before scanning the corresponding blocks. A response time ofeach pixel in the liquid crystal panel is set smaller than:

-   -   1 frame period×[[(n−1)/2n]−(1/n)] (n: odd number) or    -   1 frame period×[[(n−2)/2n]−(1/n)] (n: even number).        Therefore, the pixels complete responding with certainty before        the backlights are turned on. As a result, blurring in moving        image can be alleviated.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the scanning linesvia switching elements, a light guide plate facing the liquid crystalpanel, a first polarization splitting sheet, a liquid crystal shutterdivided along the scanning lines, a second polarization splitting sheet,a scattering element, arranged in order on one surface of the lightguide plate in this order, and a light source at one end of the lightguide plate.

Among light passing through the light guide plate (unpolarized light),an abnormal light component is reflected by the first polarizationsplitting sheet and passes through the light guide plate again. A normallight component among the unpolarized light penetrates through the firstpolarization splitting sheet and reaches the liquid crystal shutter. Inthe case where the liquid crystal shutter is in a state ofbirefringence, a phase of the light penetrated through the firstpolarization splitting sheet is shifted by 90° and the light reaches thesecond polarization splitting sheet as an abnormal light component. Thelight is then reflected by the second polarization splitting sheet andthe phase thereof is shifted by 90° by the liquid crystal shutter tobecome the original normal light component. Thereafter, the lightpenetrates through the first polarization splitting sheet and returnedto the light guide plate. On the other hand, in the case where theliquid crystal shutter is not in the state of birefringence, the lightpenetrates through the liquid crystal shutter and the secondpolarization splitting sheet as the normal light component and scatteredby the scattering element. In the case of the scattering element whichreflects light, the light irregularly reflected by the scattering sheetpenetrates through the second polarization splitting sheet, the liquidcrystal shutter, and the first polarization splitting sheet again toreturn to the light guide plate. At this time, since most components ofthe light exceed a critical angle, they penetrate through the lightguide plate to be emitted toward the liquid crystal panel. In otherwords, the light collected is emitted only from a predetermined regionof the liquid crystal shutter controlled to be in the penetrative state.

By making the predetermined region of the liquid crystal shutter tosequentially become penetrative in accordance with the control of theliquid crystal panel, impulse driving can be carried out easily.Therefore, blurring in moving image can be alleviated and flicker can beprevented. Furthermore, by collecting the light guided to the lightguide plate, the light can be used efficiently, and power consumptioncan be reduced. Since no fluorescent tubes are used, uneven display dueto degradation of the fluorescent tubes does not occur.

According to another aspect of the liquid crystal display device in thepresent invention, a change in a reflection angle at an interfacebetween neighboring materials is prevented. As a result, lighttransmitting through the light guide plate is prevented from exceeding acritical angle at a position other than a desired position.

According to another aspect of the liquid crystal display device in thepresent invention, a phase of the light passing through the light guideplate is shifted by a retardation sheet. Therefore, light not includinga normal light component comes to include the normal light component bythe shift of the phase of reflected light by the retardation sheet. Inother words, the normal light component penetrating through thepolarization splitting sheet can be increased. In this manner, efficientuse of light can be improved and power consumption can be reduced.

According to another aspect of the liquid crystal display device in thepresent invention, the light from the light guide plate is reflected bya prism and emitted toward a predetermined direction. Therefore,luminous intensity of the light can be increased.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and scanning lines for transmitting control signals arelaid out vertically and horizontally, and capacitor parts comprisingliquid crystals are arranged at intersections of the signal lines andthe scanning lines via switching elements. The liquid crystal panelcomprises resistor parts connected to the capacitor parts in paralleland having a resistance lower than a resistance of each of the capacitorparts. Therefore, an electric charge stored by writing display data isdischarged gradually via the resistor parts. In other words, withoutusing a special control circuit, impulse driving can be carried out withliquid crystal cells alone. As a result, blurring in moving image can bealleviated and flicker can be prevented.

According to another aspect of the liquid crystal display device in thepresent invention, display data are displayed at higher brightness.

According to another aspect of the liquid crystal display device in thepresent invention, uneven brightness due to a manufacturing error in asubsidiary capacitance is prevented.

According to another aspect of the liquid crystal display device in thepresent invention, the resistor parts are easily formed by using thesubsidiary capacitance added to general liquid crystal cells.

According to another aspect of the liquid crystal display device in thepresent invention, display data are reset to black by discharging anelectric charge in the capacitor parts after the data are written.Therefore, impulse driving can be realized easily without using aspecial control circuit.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare laid out at intersections of the signal lines and the scanninglines. The pixel electrodes are connected to a first TFT and a secondTFT having different threshold voltages. The gate electrodes of thefirst TFT and the second TFT connected to the pixel electrodes adjacentto each other in a direction of the scanning lines are connected to thesame scanning line. One of the TFTs is used for writing display data andthe other is used for writing reset data. Since the threshold voltage ofthe first TFT is different from the threshold voltage of the second TFT,for example, the reset data are not written when the display data arewritten. When the reset data are written, the display data are writtenin the adjacent pixel electrode, but the reset data are writtenimmediately thereafter. Therefore, wrong display data are not displayed.Impulse driving in which the display data and the reset data are writtenalternately is carried out in this manner. As a result, blurring inmoving image can be alleviated and flicker can be prevented.

According to another aspect of the liquid crystal display device in thepresent invention, each of the scanning lines is selected twice atdifferent voltages in one frame period. First, each of the scanninglines is selected at a predetermined voltage. One of the TFTs turns onand the display data are written in the corresponding pixel electrode.At this time, the other TFT is off. The scanning line is then selectedat a high voltage. The other TFT becomes on and the reset data areawritten in the corresponding pixel electrode. At this time, one of theTFTs connected to the pixel electrode next to the corresponding pixelelectrode also turns on and the display data are written. However, theother TFT connected to the neighboring pixel electrode also turns on inan immediately subsequent scan. Therefore, the display data are notdisplayed.

According to another aspect of the liquid crystal display device in thepresent invention, the display data are written in the pixel electrodevia the signal line and the first TFT. The reset data are written in thepixel electrode via an electrode to which a voltage corresponding to thereset data is supplied and via the second TFT having the thresholdvoltage higher than that of the first TFT.

According to another aspect of the liquid crystal display device in thepresent invention, the display data can be displayed at high brightnessand black data can be displayed darker.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and liquid crystalcells are arranged at intersections of the signal lines and the scanninglines, and a backlight system facing the liquid crystal panel anddivided into a plurality of luminescent parts along the scanning lines.The liquid crystal display device carries out impulse driving. In theimpulse driving, the luminescent parts are sequentially turned on, andthe scanning lines corresponding to the luminescent parts are scanned tostart writing display data in liquid crystal cells while the luminescentparts are turned off. The number of the luminescent parts, a ratio of anon-period of the luminescent parts to an off-period within one frameperiod (a duty ratio), and a response time of the liquid crystal cellsare determined so that a change in brightness during a transientresponse of the liquid crystal cells after the luminescent parts becomeon is equal to or less than 5% of the brightness at the time theluminescent parts are on. Generally, when the brightness change exceeds5%, not only blurring in an image but also ghosts in which an image isviewed as two images appear. By keeping the brightness change at 5% orless, blurring in image can be prevented and ghosts can be preventedfrom appearing. Improvement of moving image quality by adopting liquidcrystal cells having a fast response speed has been tried. However, inorder to prevent ghosts in the impulse driving, the response time of thecells, the number of the luminescent parts, and the duty ratio of theluminescent parts need to be optimal. The larger the number of theemission parts is, the more the ghosts are alleviated. The smaller theduty ratio is, the more the ghosts are prevented.

According to another aspect of the liquid crystal display device in thepresent invention, the number of lighting systems turned on at the sametime is changed in each frame and a region of the luminescent partschanges. Therefore, a boundary between the luminescent parts which areon and off becomes different in each frame. By moving the boundary ofthe luminescent parts in each frame, the boundary becomes inconspicuous.

According to another aspect of the liquid crystal display device in thepresent invention, the amount of light emitted on a phosphor layer isadjusted in accordance with a voltage supplied to the liquid crystalcells. As a result, a viewing angle becomes large and display data canbe displayed at high brightness.

According to another aspect of the liquid crystal display device in thepresent invention, the liquid crystal display device comprises a liquidcrystal panel in which a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and liquid crystalcells are laid out at intersections of the signal lines and the scanninglines, and a backlight system facing the liquid crystal panel. Theliquid crystal display device carries out impulse driving in which thescanning lines are sequentially scanned while causing the backlightsystem to blink, and the display data are written in the cells. Thedisplay data written in the liquid crystal cells in a predetermined timebefore and after the backlight system is turned off are estimate data inan on-state of the backlight system generated by carrying out motioncompensation. Therefore, the display data corresponding to the timing ofactual image display by the liquid crystal display device (at the timethe backlight system is on) are generated. As a result, blurring andawkward motion in moving image can, be prevented. In other words,quality of moving image improves.

According to another aspect of the liquid crystal display device in thepresent invention, motion compensation is carried out accurately byadopting an easy method using display data in a current frame and inanother frame.

According to one of the aspects of a method of controlling a liquidcrystal display device in the present invention, a liquid crystaldisplay device comprising a liquid crystal panel is controlled. In thisliquid crystal panel, a plurality of signal lines for transmittingdisplay data and a plurality of scanning lines for transmitting controlsignals are laid out vertically and horizontally, and pixel electrodesare arranged at intersections of the signal lines and the scanning linesvia switching elements. This panel is divided into first pixel regionsand second pixel regions adjacent to the first pixel regions. Thecontrol signals transmitted to the respective scanning lines areactivated two times each in one frame period in which an image isdisplayed, and impulse driving is carried out. The display data arewritten in the first pixel regions and the reset data are written in thesecond pixel regions when the control signals are activated once of thetwo times. The reset data are written in the first pixel regions and thedisplay data are written in the second pixel regions respectively whenthe control signals are activated the other time. By writing the resetdata in the pixel regions, the display data written in the pixel regionsimmediately before are reset. In a plurality of consecutive frames, thedisplay data written in the pixel regions are necessarily reset withinone frame period. Therefore, blurring in display image can bealleviated. Since writing and resetting the display data are carried outseparately in the first pixel regions and the second pixel regions,flicker can be prevented from occurring in a display screen.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, each backlight is turned onin synchronization with display data writing in the first pixel regionsand in the second pixel regions. Each backlight is turned off insynchronization with writing reset data in the first pixel regions andin the second pixel regions. Therefore, a contrast ratio between thecases of writing the display data and writing the reset data can beincreased and an easy-to-see screen can be configured.

According to another aspect of liquid crystal display device controllingmethod in the present invention, the period of one frame for one imageis in accordance with a period of an alternating current signal suppliedto a fluorescent tube. By writing the display data in accordance with apeak of brightness of the fluorescent tube, the contrast ratio betweenthe cases of writing and resetting the display data can be increasedwithout carrying out on-off control of the fluorescent tube.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, display data for two imagesare received in each frame. Out of the received display data, datacorresponding to the first pixel regions and the second pixel regions inwhich the reset data are written are deleted. Therefore, complex dataprocessing on display data is unnecessary. It is also unnecessary forthe display data to be stored in a buffer memory or the like.Consequently, flicker can be prevented without causing the controlcircuit to become complex.

According another aspect of the liquid crystal display devicecontrolling method of the present invention, display data for one imageare received in every frame. A portion of the display data are writtenin the first pixel regions when the control signals are activated onceof the two times, while the remaining display data are written in thesecond pixel regions when the control signals are activated the othertime. Therefore, the received data are all used as the display datawithout being deleted.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, a function of hold drivingfor activating each of the control signals once in one frame and writingdisplay data in all the pixel electrodes is used. Control of switchingbetween hold driving and impulse driving is carried out depending on animage to be displayed. For example, a moving image is displayed by usingimpulse driving while a still image is displayed by using hold driving.In this manner, optimal screen display can be realized for any image.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, a variance in brightnessbetween the cases of the hold driving and the impulse driving is reducedby increasing the brightness of the backlight upon impulse driving thanin the case of hold driving.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, gamma correction is carriedout in impulse driving and hold driving. In the impulse driving, controlsignals are activated more times than in the hold driving. Therefore, achange in the amount of light penetrating the liquid crystal cells isaccelerated by carrying out the gamma correction more rapidly in theimpulse driving than in the gamma correction in the hold driving. Inthis manner, brightness can be increased.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the scanning lines areselected according to an order the scanning lines are arranged in.Therefore, control of the scanning lines becomes easier.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the scanning lines areselected according to a predetermined order which is not related to anorder the scanning lines are arranged. Therefore, flicker can beprevented with more certainty from occurring.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the scanning lines areselected according to an order the scanning lines are arranged in thefirst pixel regions and in the second pixel regions. Therefore, withoutcausing the control of the scanning lines to become complex, flicker canbe more certainly prevented from occurring.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the liquid crystal displaydevice comprises a liquid crystal panel in which a plurality of signallines for transmitting display data and a plurality of control lines fortransmitting control signals are laid out vertically and horizontally,and pixel electrodes are arranged via switching elements atintersections of the signal lines and the control lines. The liquidcrystal display device carries out gamma correction in response to atemperature change of the liquid crystal panel. Therefore, regardless ofthe temperature change of the liquid crystal panel, brightness andcontrast of a display screen are constant.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the controlling methodcontrols a liquid crystal display device comprising a liquid crystalpanel in which a plurality of signal lines for transmitting display dataand a plurality of control lines for transmitting control signals arelaid out vertically and horizontally, and pixel electrodes are arrangedvia switching elements at intersections of the signal lines and thecontrol lines, a plurality of first backlights arranged on the backsideof the liquid crystal panel and separated from each other, and aplurality of second backlights each adjacent to the first backlights andseparated from each other. In other words, by turning on and off thefirst backlights and the second backlights, pseudo-impulse driving canbe realized. Image blurring can be alleviated and flicker can thus beprevented from occurring.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, a luminescent period inwhich a display image in one frame period is output can be adjustedmanually. Therefore, a viewer of the display image can directly adjustthe display image for optimal view of the image. For example, theluminescent period is lengthened when a still image is viewed, whileshortened when a moving image is viewed. Since the liquid crystaldisplay device is adjustable in accordance with how the viewer of thedisplay image feels, blurring in moving image can be alleviated andflicker can be prevented.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, a luminescent period inwhich a display image in one frame period is output can be adjusted inaccordance with a speed of motion of an image displayed on the liquidcrystal panel. Therefore, blurring in moving image can be alleviated byshortening the luminescent period in the case of displaying a movingimage and flicker can be prevented.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, a data driver outputsdisplay data to signal lines while a timing signal is active. A gatedriver sequentially outputs gate pulses to scanning lines. Switchingelements are controlled by the gate pulses, and the display data orreset data are written in pixel electrodes at intersections of thesignal lines and the scanning lines. The data driver outputs the displaydata in an active period of the timing signal in one horizontal period,and outputs the reset data in an inactive period of the signal. Bycontrolling the gate driver in accordance with the output timings of thedisplay data and the reset data and by writing the data in one frameperiod, impulse driving can be carried out. As a result, blurring in amoving image can be alleviated and flicker can be prevented fromoccurring.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the reset data are writtenin the beginning of the one horizontal period and the display data arewritten consecutively thereafter. In other words, the display data arewritten over the reset data. As a result, the gate pulses for writingthe display data can be formed easily.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, width of the gate pulsesfor writing the reset data can be widened sufficiently and the resetdata can be written with certainty.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, a conventional data driverfor generating display data, for example, can be used as it is forimpulse driving.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, AC driving can be carriedout for also the reset data.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, the reset data can bewritten with certainty.

According to another aspect of the liquid crystal display devicecontrolling method in the present invention, reset data are also writtenin a blanking period. Therefore, the reset data are always written aftera certain amount of time has elapsed since display data writing. As aresult, in each pixel electrode, display data are displayed for the sameduration and a period of displaying the reset data becomes equal.Therefore, brightness of the display data in the panel can be uniformedand brightness can be prevented from becoming uneven.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature, principle, and utility of the invention will become moreapparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by identical reference numbers, in which:

FIG. 1 is a block diagram showing an outline of a conventional liquidcrystal display device;

FIG. 2 is a timing chart showing a state of writing display data in theliquid crystal display device in FIG. 1;

FIG. 3 is a timing chart showing a waveform of a driving voltage in aconventional CRT;

FIG. 4 is a timing chart showing a state of impulse driving carried outin a conventional liquid crystal display device;

FIG. 5 shows an example of a display screen in the case of the impulsedriving shown in FIG. 4;

FIG. 6 is a block diagram-showing a basic principle of a liquid crystaldisplay device of the present invention and a controlling methodthereof;

FIG. 7 is a block diagram showing a basic principle of another liquidcrystal display device of the present invention and a controlling methodthereof;

FIG. 8 is a block diagram showing a basic principle of another liquidcrystal display device of the present invention and a controlling methodthereof;

FIG. 9 is a block diagram showing a first embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 10 shows a state of writing display data in the liquid crystaldisplay device shown in FIG. 9;

FIG. 11 is a block diagram showing a second embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 12 shows a state of writing display data in the liquid crystaldisplay device shown in FIG. 11;

FIG. 13 is a block diagram showing a third embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 14 shows a state of writing display data in the liquid crystaldisplay device shown in FIG. 13;

FIG. 15 shows a state in which fluorescent tubes are turned on and offin the liquid crystal display device shown in FIG. 13;

FIG. 16 is a block diagram showing a fourth embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 17 shows a state of writing display data in the liquid crystaldisplay device shown in FIG. 16;

FIG. 18 shows a state in which light-emitting diodes are turned on andoff in the liquid crystal display device shown in FIG. 16;

FIG. 19 is a block diagram showing a fifth embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 20 shows a state in which fluorescent tubes are turned on and offin the liquid crystal display device shown in FIG. 19;

FIG. 21 is a block diagram showing a sixth embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 22 is a block diagram showing a seventh embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 23 is a timing chart showing a state of writing display data in theliquid crystal display device shown in FIG. 22;

FIG. 24 is a block diagram showing an eighth embodiment of the liquidcrystal display device of the present invention and the controllingmethod thereof;

FIG. 25 is a timing chart showing a state in which display data arewritten in the liquid crystal display device shown in FIG. 24;

FIG. 26 is a block diagram showing a ninth embodiment of the liquidcrystal display device of the present invention;

FIG. 27 is a timing chart showing a state in which display data arewritten in the liquid crystal display device shown in FIG. 26;

FIG. 28 is a block diagram showing a tenth embodiment of the liquidcrystal display device of the present invention;

FIG. 29 is a timing chart showing a state in which display data arewritten in the liquid crystal display device shown in FIG. 28;

FIG. 30 is a block diagram showing a ninth embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 31 is a block diagram showing a tenth embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 32 is a block diagram showing an eleventh embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 33 is a block diagram showing an eleventh embodiment of the liquidcrystal display device of the present invention;

FIG. 34 is a diagram showing a backlight shown in FIG. 33 in detail;

FIG. 35 is a diagram showing control of a liquid crystal liquid crystalpanel and a backlight;

FIG. 36 is a diagram showing in detail a backlight in a twelfthembodiment of the liquid crystal display device of the presentinvention;

FIG. 37 is a diagram showing control of a liquid crystal liquid crystalpanel and a backlight;

FIG. 38 is a diagram showing another example of the backlight;

FIG. 39 is a diagram showing in detail a backlight in a thirteenthembodiment of the liquid crystal display device of the presentinvention;

FIG. 40 is a diagram showing a liquid crystal film in shown FIG. 39 indetail;

FIG. 41 is a diagram showing an ordinary liquid crystal film in detail;

FIG. 42 is a diagram showing in detail a backlight in a fourteenthembodiment of the liquid crystal display device of the presentinvention;

FIG. 43 is a block diagram showing a fifteenth embodiment of the liquidcrystal display device and a twelfth embodiment of the liquid crystaldisplay device controlling method of the present invention;

FIG. 44 is a block diagram showing a sixteenth embodiment of the liquidcrystal display device and a thirteenth embodiment of the liquid crystaldisplay device controlling method of the present invention;

FIG. 45A is a block diagram showing a seventeenth embodiment of theliquid crystal display device of the present invention;

FIG. 45B is a block diagram showing another example of the liquidcrystal display device;

FIG. 46 is a diagram showing an eighteenth embodiment of the liquidcrystal display device of the present invention;

FIG. 47 is a diagram showing a nineteenth embodiment of the liquidcrystal display device of the present invention;

FIG. 48 is a diagram showing the detail of FIG. 47;

FIG. 49 is a diagram showing a twentieth embodiment of the liquidcrystal display device of the present invention;

FIG. 50 is a diagram showing a twenty-first embodiment of the liquidcrystal display device of the present invention;

FIG. 51 is a diagram showing a twenty-second embodiment of the liquidcrystal display device of the present invention;

FIG. 52 is a diagram showing a twenty-third embodiment of the liquidcrystal display device of the present invention;

FIG. 53 is a diagram showing a twenty-fourth embodiment of the liquidcrystal display device of the present invention;

FIG. 54 is a block diagram showing a twenty-fifth embodiment of theliquid crystal display device of the present invention;

FIG. 55 is a cross-section showing a liquid crystal cell in detail;

FIG. 56 is an equivalent circuit of the liquid crystal cell;

FIG. 57 shows a state in which display data are written in the liquidcrystal cell;

FIG. 58 shows changes in a supplied voltage in accordance with a CR timeconstant of the equivalent circuit;

FIG. 59 shows changes in a supplied voltage in relation to a CR constantof amorphous silicon;

FIG. 60 shows changes in a supplied voltage in relation to a layerthickness and an area of the amorphous silicon;

FIG. 61 shows changes in a supplied voltage in relation to a change inthe layer thickness of the amorphous silicon;

FIG. 62 is a block diagram showing a twenty-sixth embodiment of theliquid crystal display device of the present invention;

FIG. 63 is a cross-section showing a detailed structure of a TFT (ThinFilm Transistor);

FIG. 64 shows an operation of a liquid crystal panel;

FIG. 65 is a block diagram showing a twenty-seventh embodiment of theliquid crystal display device of the present invention;

FIG. 66 is a block diagram showing a fourteenth embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 67 is a block diagram showing a control circuit in detail;

FIG. 68 is a timing chart showing an operation of the control circuit;

FIG. 69 is a timing chart showing an operation of a liquid crystalpanel;

FIG. 70 shows an outline of display of the liquid crystal displaydevice;

FIG. 71 is a timing chart showing a fifteenth embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 72 is a timing chart showing a sixteenth embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 73 is a timing chart showing a seventeenth embodiment of the liquidcrystal display device controlling method of the present invention;

FIG. 74 is a block diagram showing a twenty-eighth embodiment of theliquid crystal display device of the present invention;

FIG. 75 shows a ground for determining each condition of the liquidcrystal display device;

FIG. 76 shows a reference for the case of measuring a response time of aliquid crystal;

FIG. 77 shows conditions for not causing ghosts or blurring in an image;

FIG. 78 is a block diagram showing a twenty-ninth embodiment of theliquid crystal display device of the present invention;

FIG. 79 shows how a luminescent part is formed;

FIG. 80 is a block diagram showing a thirtieth embodiment of the liquidcrystal display device of the present invention;

FIG. 81 is a block diagram showing an interpolating circuit in detail;and

FIG. 82 shows an outline of an operation and motion compensation of theliquid crystal display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained withreference to the accompanying drawings.

FIG. 6 is a block diagram showing a basic principle of a liquid crystaldisplay device of the present invention and a method of controlling theliquid crystal display device.

The liquid crystal display device comprises a liquid crystal panel A inwhich a plurality of signal lines D1–Dm for transmitting display dataand a plurality of scanning lines G1–Gn for transmitting control signalsare laid out vertically and horizontally and pixel electrodes 5 arearranged via switching elements 4 at intersections of the signal linesand the scanning lines, and a control circuit 6 for controlling theliquid crystal panel A via the signal lines D1–Dm and the scanning linesG1–Gn. The liquid crystal panel A is divided into first pixel regions 7and second pixel regions 8 next to the pixel regions 7.

The control circuit 6 carries out impulse driving in which the controlsignals transmitted to the respective scanning lines are activated twotimes each in one frame period in which one image is displayed. Thecontrol circuit 6 writes display data in the first pixel regions 7 andreset data in the second pixel regions 8 when the control signals areactive at one of the two times. The control circuit 6 also writes thereset data in the first pixel regions 7 and the display data in thesecond pixel regions 8 when the control signals are active at the othertime. By writing the reset data in the first pixel regions 7 and thesecond pixel regions 8, display data written therein immediately beforeare reset. In consecutive frames, the display data written in the firstpixel regions 7 and the second pixel regions 8 are always reset in oneframe period. Therefore, blurring in a display image is alleviated.Since writing and resetting of the display data are carried outseparately in the first pixel regions 7 and the second pixel regions 8,flicker is prevented from occurring in a display screen.

Furthermore, as shown in FIG. 6, the display data and the reset data arewritten sequentially in the first pixel regions 7 and the second pixelregions 8 divided in stripes along the scanning lines. The regions forwriting the reset data are divided into the plurality of pixel regions 7and 8. Therefore, blurring in a display image is alleviated and flickeris prevented from occurring in the display screen.

FIG. 7 is a block diagram showing a basic principle of another liquidcrystal display device of the present invention and a controlling methodof the liquid crystal display device.

In the liquid crystal display device, the first pixel regions 7 and thesecond pixel regions 8 are divided into a lattice-like form. The displaydata and the reset data are sequentially written in the first pixelregions 7 and the second pixel regions 8 divided into a lattice-likeform. The regions in which the reset data are written are divided intothe plurality of the first pixel regions 7 and the second pixel regions8. Therefore, blurring in a display image is alleviated and flicker isprevented from occurring in the display screen.

FIG. 8 is a block diagram showing a basic principle of another liquidcrystal display device of the present invention and a method ofcontrolling the liquid crystal display device.

The liquid crystal display device comprises backlights 9 on the backsideof the liquid crystal panel A, facing the first pixel regions 7 and thesecond pixel regions 8. Each of the backlights 9 is turned on insynchronization with writing the display data in the first pixel regions7 and the second pixel regions 8. Each of the backlights 9 is turned offin synchronization with writing the reset data in the first pixelregions 7 and the second pixel regions 8. Therefore, a contrast ratiobetween the cases of writing display data and writing reset data can beincreased and an easy-to-see screen can be configured. Furthermore,since the backlights 9 corresponding to the pixel regions 7 and 8 inwhich the display data are not written are turned off, power consumptioncan be reduced.

The First embodiment of the Liquid Crystal Display Device and the FirstEmbodiment of the Liquid Crystal Display Device Controlling Method

FIG. 9 shows an outline of a TFT (Thin Film Transistor) driving liquidcrystal display device used in this embodiment.

This device comprises TFTs and pixel electrodes 12 laid out in the formof a matrix. Gate electrodes of the TFTs which are switching elementsare connected to the scanning lines G1–Gn. The scanning lines G1–Gn arelines for transmitting gate signals output from a Y driver 14. Drainelectrodes of the TFTs are connected to the signal lines D1–Dm. Thesignal lines D1–Dm are signal lines for transmitting data signals froman X driver 16. The source electrodes of the TFTs are connected to thepixel electrodes 12.

Counter electrodes (not shown) are arranged, facing the pixel electrodes12. Liquid crystals (not shown) are sandwiched by the pixel electrodes12 and the counter electrodes, forming liquid crystal cells C. Theliquid crystal panel A is formed with liquid crystal cells C arrangedvertically and horizontally. In this embodiment, the liquid crystalcells C are formed with π cells having a short response time such as 2ms, for example. For the liquid crystal liquid crystal panel A, otherliquid crystal display modes, such as a TN (Twisted Nematic) type LCD oran LCD of in-plane switching mode can be used.

The Y driver 14 and the X driver 16 are controlled by a control circuit18. The control circuit 18 receives the display data from exterior. TheY driver 14, the X driver 16, and the control circuit 18 correspond tothe control circuit 6 shown in FIG. 6.

The liquid crystal panel A is divided into a plurality of first pixelregions 20 spaced out evenly and a plurality of second pixel regions 22separated from each other and each adjacent to the first pixel regions20. The first pixel regions 20 and the second pixel regions 22 areformed in the form of stripes along the scanning lines.

FIG. 10 shows a state in which the display data are written in theliquid crystal display device described above. The liquid crystal panelA has 6 pixels and 8 pixels in the vertical direction and in thehorizontal direction respectively, for the sake of simpler explanation.In other words, the liquid crystal panel A is driven by the 6 scanninglines G1–G6 and the 8 signal lines D1–D8.

The scanning lines G1–G6 are respectively activated twice in one frameperiod (16 ms) in which one image is displayed, as shown by thewaveforms in FIG. 10. The scanning lines transmit high level-pulse gatesignals to the liquid crystal panel A. Therefore, each of the liquidcrystal cells C can display two data in one frame period. The Y driver14 shown in FIG. 9 carries out a so-called “line-sequential scanning” toactivate the scanning lines G1–G6 in the order of an arrangement whileshifting the phases of each of the gate signals. Therefore, the controlcircuit such as the Y driver can be configured without substantiallychanging a conventional circuit. Within one frame period, a period inwhich the scanning lines G1–G6 are activated for the first time iscalled a first field and a period in which the scanning lines G1–G6 areactivated for the second time is called a second field in thisspecification.

The control circuit 18 shown in FIG. 9 receives display data for twoimages in one frame period. The control circuit 18 writes in the firstpixel regions 20 data corresponding to these regions 20 out of thedisplay data having been received, and writes black data in the secondpixel regions 22 as the reset data. The cells in which the display dataare written are shown by white cells and cells in which the black dataare =written are shown by hatched areas. As a result, as shown in adisplay screen in FIG. 10( a), the display data are written in everyother line corresponding to one scanning line at the end of the firstfield. For example, the amount of penetrating light increases in thefirst field in the cell C shown by a bold frame where the scanning lineG1 and the signal line D1 intersect, as shown in FIG. 10. Therefore,white is displayed.

The control circuit 18 deletes the display data corresponding to thesecond pixel regions 22 out of the display data having been receivedfirst and writing black data instead of the display data. Conversion ofthe display data to the black data can be carried out by a simple gatecircuit. In this embodiment, it is unnecessary for the portion of thedisplayed data to be stored in a buffer memory or the like. Therefore, acircuit necessary for the conversion processing in the control circuit18 can be minimized. Furthermore, the control of conversion to the blackdata can be carried out easily.

In the second field, the control circuit 18 then writes in the secondpixel regions 22 data corresponding thereto out of the display datareceived in the second time, and writes the black data in the firstpixel regions 20 as the reset data. The control circuit 18 deletes thedisplay data corresponding to the first pixel regions 20 out of thedisplay data received in the first time, and writes the black datainstead of the display data. As a result, as shown by a display screenin FIG. 10( b), display of the first pixel regions 20 in which thedisplay data were written in the first field is reset by the black data.

The control circuit 18 alternately resets (black) the display datawritten in the first pixel regions 20 and the second pixel regions 22 byrepeating the writing operations described above. Therefore, blurringsuch as tailing in a moving image can be prevented from occurring.

A display screen shown in FIG. 10( c) shows a state in which thescanning line G3 is activated in the first field. The lines where thedisplay data are displayed over a plurality of the scanning linesadjacent to each other are the lines controlled by the line G3 and itsneighboring line. In other lines, the display data and the black dataare displayed alternately.

A display screen shown in FIG. 10( d) shows a state in which thescanning line G4 is activated in the first field. The lines where theblack data are displayed over a plurality of the scanning lines adjacentto each other are the lines controlled by the line G4 and a neighboringline thereof. In other lines, the display data and the black data aredisplayed alternately.

As has been described above, the display data and the black data arewritten separately in the first pixel regions 20 and the second pixelregions 22 rather than one undivided area in the panel 20. Therefore,flicker is prevented from occurring in the display screen.

As has been described above, according to the liquid crystal displaydevice and the controlling method of the present invention, the liquidcrystal panel A is divided into a plurality of the first pixel regions20 and the second pixel regions 22 separated from each other, and thedisplay data and the reset data are written alternately in these areas20 and 22. Therefore, blurring in a display image can be alleviated andflicker is prevented from occurring.

The control circuit 18 carries out conversion processing from thedisplay data to the black data by deleting a portion of the display dataand writing the black data instead of the deleted display data.Therefore, the conversion processing can be carried out by a simple gatecircuit in the control circuit 18. Consequently, the size of the controlcircuit 18 can be minimized and the conversion processing can becontrolled easily.

Since the scanning lines G1–G6 are subjected to line-sequential scanningas in a conventional device, the control circuit such as the Y driver 14can be configured without a substantial change in a conventionalcircuit. In other words, the scanning lines are controlled easily.

In this embodiment, the liquid crystal panel A comprises the π cellshaving the 2-ms response time. However, the present invention is notlimited to this example, and liquid crystal cells having a 16-msresponse time may be used. In this case, the same effect as by the firstembodiment can be obtained by setting the period of one frame to 32 ms,for example. As the liquid crystal cells, VA (Vertical Alignment) typecells having vertical alignment and partially including an electricfield horizontal to the panel with anisotropy of the dielectric constantE being positive may be used. Alternatively, MVA (Multi-domain VerticalAlignment) type cells having vertical alignment, and a vertical electricfield, with anisotropy of a negative dielectric constant ε, or IPS (InPlane Switching) type cells having horizontal alignment and a horizontalelectric field may be used.

The second Embodiment of the Liquid Crystal Display Device and theSecond Embodiment of the Liquid Crystal Display Device ControllingMethod

In this embodiment, elements corresponding to the elements describedabove for the first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

FIG. 11 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, the first pixel regions 20 and the second pixel regions 22are in a lattice-like form of each liquid crystal cell C. A controlcircuit 24 comprises a buffer memory 24 a for retaining a portion of thedisplay data transmitted from exterior. Other configurations are thesame as in the first embodiment.

FIG. 12 shows a state in which display data are written in the liquidcrystal display device described above.

In this embodiment, the control circuit 24 shown in FIG. 11 receivesdisplay data for one image in one frame period (16 ms). In the firstfield, the control circuit 24 writes in the pixel regions 20 datacorresponding thereto out of the display data having been received, andwrites black data in the second pixel regions 22 as the reset data. Inother words, the control circuit 24 alternately outputs the display dataand the black data as the reset data to the X driver 16. The displaydata and the reset data are respectively transmitted to every othersignal line. The control circuit 24 temporarily retains in the buffermemory 24 a a portion of the display data corresponding to the secondpixel regions 22 in which the black data are written in the first field.Control of the scanning lines G1–Gn by the Y driver 14 is the same as inthe first embodiment.

As a result, as a display screen shown in FIG. 12( a), data in a checkpattern are displayed on the liquid crystal panel A at the end of thefirst field. For example, the amount of light penetrating through one ofthe cells C shown by a bold frame where the scanning line G1 and thesignal line D1 intersect increases as shown by the waveform in the firstfield, and white is displayed.

In the second field, the control circuit 24 then reads the display datahaving been retained in the buffer memory 24 a. The control circuit 24writes the data in the second pixel regions 22 while writing black datain the first pixel regions 20 as the reset data. As a result, as in adisplay screen shown in FIG. 12( b), the first pixel regions 20 in whichthe display data were written in the first field are reset by the blackdata.

The control circuit 24 alternately resets (black) the display datawritten in the first pixel regions 20 and the second pixel regions 22 byrepeating the writing operations described above. Therefore, blurringsuch as tailing in a moving image can be prevented.

A display screen shown in FIG. 12( c) shows a state in which thescanning line G3 is activated in the first field. The only cells inwhich the display data are displayed over a plurality of the lines areevery other cell in the line controlled by the scanning line G3 and itsneighboring line. Therefore, the display data are not displayed inconsecutive cells C in the direction of the scanning line, and thedisplay data and the black data are alternately displayed in otherlines.

A display screen shown in FIG. 12( d) shows a state in which thescanning line G4 is activated in the first field. The only cells inwhich the black data are displayed over a plurality of the lines areevery other cell in the line controlled by the scanning line G4 and itsneighboring line. Therefore, the black data are not displayed inconsecutive cells C in the direction of the scanning line, and thedisplay data and the black data are alternately displayed in otherlines.

As has been described above, writing the display data and the reset datais carried out separately and alternately in the first pixel regions 20and in the second pixel regions 22 (in other words, in each of the cellsC). Therefore, flicker is prevented from occurring in the displayscreen.

In this embodiment, the same effect as by the first embodiment can beobtained. Furthermore, in this embodiment, the first pixel regions 20and the second pixel regions 22 are further divided along the scanningline. Therefore, flicker is prevented with certainty from occurring inthe display screen.

The Third Embodiment of the Liquid Crystal Display Device and the ThirdEmbodiment of the Liquid Crystal Display Device Controlling Method

FIG. 13 shows a configuration of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above inthe first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

In this embodiment, the liquid crystal panel A comprises the two firstpixel regions 20 and the two second pixel regions 22 arrangedalternately in the form of stripes.

Each of the first pixel regions 20 and the second pixel regions 22 isdivided according to liquid crystal cells C corresponding to twoscanning lines. The liquid crystal panel A is assumed to have 8 pixelsin vertical direction and 8 pixels in horizontal direction, for the sakeof simpler explanation. In reality, the height and the width of theliquid crystal cells C are approximately 0.3 mm each. Each of the firstpixel regions 20 and the second pixel regions 22 is actually dividedaccording to, the liquid crystal cells C corresponding to several totens of lines or hundreds or thousands of lines.

On the backside of the liquid crystal panel A, light guide plates 26made of a transparent resin such as polycarbonate are arranged atpositions facing the first pixel regions 20 and the second pixel regions22. Surfaces of the light guide plates 26 where these light guide plates26 are in contact with each other have minute irregularities. By theseirregularities, light guided thereto is irregularly reflected and jointsbetween the light guide plates 26 become inconspicuous. Fluorescenttubes F1–F4 as backlights are arranged at one end of each of the lightguide plates 26 in the longitudinal direction. Other configurations arethe same as in the first embodiment, except for a control circuit (notshown) having a function of controlling the fluorescent tubes F1–F4.

FIG. 14 shows a state in which display data are written in the liquidcrystal display device described above.

The scanning lines G1–G8 are activated twice in one frame period (16 ms)in which one image is displayed, as shown by the waveforms in FIG. 14.In this manner, a so-called sequential line scanning is carried out. Inthe first field, data corresponding to the first pixel regions 20 out ofthe display data are written in the first pixel regions, and black dataare written in the second pixel regions 22 as the reset data. In thesecond field, data corresponding to the second pixel regions 22 out ofthe display data are written in the second pixel regions 22, and blackdata are written in the first pixel regions 20 as the reset data.

The fluorescent tubes F1–F4 are controlled in accordance with thecontrol of the scanning lines G1–G8. For example, in the first field,the fluorescent tube F1 is turned on in synchronization with activationof the scanning line G1. The fluorescent tube F3 is turned on insynchronization with activation of the scanning line G5. Likewise, thefluorescent tubes F2 and F4 are turned off in synchronization withactivation of the scanning lines G4 and G8, respectively. In the secondfield, the fluorescent tubes F1 and F3 are respectively turned off insynchronization with activation of the scanning line G2 and G6, and thefluorescent tubes F2 and F4 are turned on in synchronization withactivation of the scanning lines G3 and G7, respectively.

A display screen shown in FIG. 14( a) shows a state in which thescanning line G8 is activated in the first field. The fluorescent tubesF1 and F3 which are turned on are shown in white. Likewise, a displayscreen shown in FIG. 14( b) shows a state in which the scanning line G8is activated in the second field. In other words, in this embodiment,the fluorescent tubes corresponding to the first pixel regions 20 andthe second pixel regions 22 in which display data are written are turnedon while the fluorescent tubes corresponding to the first pixel regions20 and the second pixel regions 22 in which black data are written areturned off. This control is carried out by the control circuit which isnot shown. As a result, brightness at the time the black data aredisplayed decreases and the contrast ratio between the display data andthe black data increases. Therefore, an easy-to-see screen can beconfigured. Furthermore, since the fluorescent tubes corresponding tothe first pixel regions 20 and the second pixel regions 22 in which thedisplay data are not displayed are turned off, power consumption isreduced.

FIGS. 15( a) and 15(b) show states in which the scanning line G3 isactivated in the first field and in the second field, respectively.

In FIG. 15( a), the fluorescent tube T2 is not turned off at the timethe black data are written in the line corresponding to the scanningline G3. This is because the display data are displayed in the linecorresponding to the scanning line G4 when the scanning line G3 isactivated in the first field. As shown by the waveforms in FIG. 14, thefluorescent tube F2 is turned off in synchronization with activation ofthe scanning line G4.

On the contrary, the fluorescent tube F2 is turned on in synchronizationwith activation of the scanning line G3 as in FIG. 15( b). This isbecause the display data are displayed in the line corresponding to thescanning line G3 when the scanning line G3 is active in the secondfield. By the timings of turning on and off the fluorescent tubes,brightest display can be realized.

In this embodiment, the same effect as by the first embodiment can beobtained. Furthermore, in this embodiment, the backlights are arrangedon the backside of the liquid crystal panel A. Therefore, the contrastratio between the case of writing the display data and the case ofwriting the black data as the reset data can be increased and aneasy-to-see screen can be configured.

Since the fluorescent tubes F1–F4 are used, the backlights can beconfigured easily in accordance with the first pixel regions 20 and thesecond pixel regions 22.

Moreover, the light guide plates 26 are used in accordance with the sizeof the first pixel region 20 and the second pixel region 22, and thenumber of the fluorescent tubes to be used can be minimized.

In this embodiment, the fluorescent tubes F1–F4 are turned off afterbeing turned on. However, the present invention is not limited to thisexample, and brightness of the fluorescent tubes F1–F4 may be weakenedinstead of completely turning off the fluorescent tubes.

The Fourth Embodiment of the Liquid Crystal Display Device and theFourth Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 16 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

In this embodiment, the liquid crystal panel A is divided inlattice-like form, into four first pixel regions 20 and four secondpixel regions 22 adjacent to each other. For simpler explanation, theliquid crystal panel A is assumed to have 8 pixels in the verticaldirection and 8 pixels in the horizontal direction. Light-emittingdiodes L1–L8 are arranged on the backside of the liquid crystal panel Aat positions facing the first pixel regions 20 and the second pixelregions 22. In other words, each of the light-emitting diodes L1–L8 isarranged corresponding to an area of 2 pixels in the vertical directionand 4 pixels in the horizontal direction. In reality, the first pixelregions 20 and the second pixel regions 22 are divided corresponding totens or hundreds of the liquid crystal cells C. Configurations otherthan the above are the same as in the first embodiment, except for acontrol circuit (not shown) having a function of controlling thelight-emitting diodes L1–L8.

As in the third embodiment described above, fluorescent tubes and lightguide plates may be used instead of the light-emitting diodes L1–L8.

FIG. 17 shows a state in which display data are written in the liquidcrystal display device.

As shown by waveforms in FIG. 17, the scanning lines G1–G8 are activatedtwice in one frame period (16 ms) in which an image is displayed, andthe so-called line-sequential scanning is carried out. In the firstfield, data corresponding to the first pixel regions 20 out of thedisplayed data are written in the first pixel regions 20, and the blackdata as the reset data are written in the second pixel regions 22. Inthe second field, data corresponding to the second pixel regions 22 outof the display data are written in the second pixel regions 22 and theblack data as the reset data are written in the first pixel regions 20.

The light-emitting diodes L1–L8 are controlled in accordance with thecontrol of the scanning lines G1–G8. For example, in the first field,the light emitting diode L1 is turned on in synchronization withactivation of the scanning line G1. The light-emitting diodes L6, L3 andL8 are turned on in synchronization with activation of the scanninglines G3, G5 and G7. Likewise, the light-emitting diodes L5, L2, L7, andL4 are turned off in synchronization with activation of the scanninglines G2, G4, G6, and G8. In the second field, the light-emitting diodesL5, L2, L7, and L4 are turned on in synchronization with activation ofthe scanning lines G1, G3, G5, and G7. In synchronization withactivation of the scanning lines G2, G4, G6, and G8, the light-emittingdiodes L1, L6, L3, and L8 are turned off.

A display screen shown in FIG. 17( a) shows a state in which thescanning line G8 is activated in the first field. The light-emittingdiodes L1, L3, L6, and L8 which are on are shown in white. Likewise, adisplay screen shown in FIG. 17( b) shows a state in which the scanningline G8 is activated in the second field. In other words, in thisembodiment, the light-emitting diodes corresponding to the first pixelregions 20 and the second pixel regions 22 in which the display data arewritten are turned on. This control is carried out by the controlcircuit which is not shown.

FIGS. 18( a) and 18(b) show states in which the scanning line G3 isactivated in the first field and in the second field, respectively.

In FIG. 18( a), the light emitting diode L2 is not turned off in thecase where black data are written in the line corresponding to thescanning line G3. This is because display data are displayed in the linecorresponding to the scanning line G4 at the time of activation of thescanning line G3 in the first field. The light emitting diode L2 isturned off in synchronization with activation of the scanning line G4,as shown by the waveforms in FIG. 17. On the contrary, the lightemitting diode L2 is turned on when the scanning line G3 is activated.This is because the display data are displayed in the line correspondingto the scanning line G3.

On the other hand, in FIG. 18( b), the light emitting diode L2 is turnedon in synchronization with activation of the scanning line G3. This isbecause the display data are displayed in the line corresponding to thescanning line G3 at the time of activation of the scanning line G3 inthe second field.

In this embodiment, the same effects as by the third embodiment can beobtained.

In this embodiment, the light-emitting diodes L1–L8 are used as thebacklights. However, the present invention is not limited to thisexample. For example, the backlights can be formed by using a PDP(Plasma Display Panel). In this case, a multitude of the first pixelregions 20 and the second pixel regions 22 each having a small area canbe used.

The Fifth Embodiment of the Liquid Crystal Display Device and the FifthEmbodiment of the Liquid Crystal Display Device Controlling Method

FIG. 19 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe first embodiment and for the third embodiment are given the samereference numerals and explanation of these elements is not repeated.

In this embodiment, the liquid crystal panel A has the two first pixelregions 20 and the two second pixel regions 22 arranged in alternationin stripes. For simpler explanation, the first pixel regions 20 and thesecond pixel regions 22 are divided according to the liquid crystalcells C corresponding to one line. In reality, the first pixel regions20 and second pixel regions 22 are divided according to the liquidcrystal cells C corresponding to tens to hundreds, or hundreds tothousands of lines. The fluorescent tubes F1–F4 are arranged on thebackside of the liquid crystal panel A, each facing the first pixelregions 20 and the second pixel regions 22. In reality, each of thefluorescent tubes F1–F4 is formed with a plurality of tubes laid out inparallel in the direction of the scanning lines. A control circuit 30controls the Y driver 14, the X driver 16, and the fluorescent tubesF1–F4. The control circuit 30 has a function of supplying an AC voltagehaving a predetermined frequency to each of the fluorescent tubes F1–F4while shifting the phase thereof.

FIG. 20 shows a state in which the fluorescent tubes F1–F4 are turned onand off and the scanning lines G1–G8 are driven in the liquid crystaldisplay device described above.

Each of the fluorescent tubes F1–F4 emits light in the same period, witha predetermined phase shift.

Therefore, a phase of maximum brightness is different between thefluorescent tubes F1–F4, and so is a phase of minimum brightness. Thecontrol circuit 30 shown in FIG. 19 causes one frame period tosynchronize with the luminescent period of the fluorescent tubes F1–F4and activates each of the scanning lines G1–G4 at timings slightlybefore the timings of maximum and minimum brightness of, the fluorescenttubes F1–F4. More specifically, the scanning line G1 is activatedslightly before the time the fluorescent tube F1 has the maximumbrightness in the first field, and activated again slightly before thetime the fluorescent tube F1 has the minimum brightness in the secondfield. The scanning line G2 is activated slightly before the time thefluorescent tube F2 has the minimum brightness in the first field, andactivated again slightly before the time the fluorescent tube F2 has themaximum brightness in the second field. The scanning line G3 isactivated slightly before the time the fluorescent tube F3 has themaximum brightness in the first field, and activated again slightlybefore the time the fluorescent tube F3 has the minimum brightness inthe second field. The scanning line G4 is activated slightly before thetime the fluorescent tube F4 has the minimum brightness in the firstfield, and activated again slightly before the time the fluorescent tubeF4 has the maximum brightness in the second field.

In the first field, by activation of the scanning lines G1 and G3,display data are written in the first pixel regions 20 shown in FIG. 19.By activation of the scanning lines G2 and G4, black data are written inthe second pixel regions 22. In the first field, by activation of thescanning lines G1 and G3, black data are written in the first pixelregions 20. By activation of the scanning lines G2 and G4, display dataare written in the second pixel regions 22.

Therefore, brightness of the fluorescent tubes F1–F4 becomes maximalimmediately after writing the display data, and becomes minimalimmediately after writing the black data. As a result, without specialon-off control of the fluorescent tubes F1–F4, an image having a highcontrast ratio and no flicker can be displayed.

In this embodiment, the same effect as by the first embodiment can beobtained. Furthermore, in this embodiment, the control circuit 30controls the scanning lines G1–G4 by causing one frame period tosynchronize with the period of the AC voltage supplied to thefluorescent tubes F1–F4. Therefore, without special on-off control ofthe fluorescent tubes F1–F4, the contrast ratio of the screen can beincreased.

The Sixth Embodiment of the Liquid Crystal Display Device and the SixthEmbodiment of the Liquid Crystal Display Device Controlling Method

FIG. 21 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe first embodiment and for the third embodiment are given the samereference numerals and explanation of these elements is not repeated.

In this embodiment, a control circuit 32 has a hold driving circuit 34,an impulse driving circuit 36 and a gamma correction table 38.Configurations other than the above are the same as in the fifthembodiment.

The gamma correction table 38 has correction data for hold driving andimpulse driving and correction data corresponding to a temperature ofthe liquid crystal panel A.

The control circuit 32 activates the impulse driving circuit 36 when amoving image is displayed and activates the hold driving circuit 34 whena still image is displayed. In other words, in this embodiment, holddriving and impulse driving can be switched from one to another,depending on a display screen. The still image is not limited to aphotograph. For example, if the liquid crystal display device of thepresent invention is connected to a personal computer, a screendisplayed by software, such as a spread sheet used on the computer, isdealt with as the still image.

When the impulse driving in which the display data are displayed at alow rate in one frame period is carried out, the control circuit 32increases the brightness of the fluorescent tubes F1–F4 than in the caseof the hold driving. Therefore, variance in the brightness between thecase of the impulse driving and the case of the hold driving can bereduced.

The control circuit 32 carries out optimal gamma correction at the timeof the hold driving and the impulse driving.

Furthermore, the control circuit 32 receives the temperature of theliquid crystal panel A as a temperature detection signal and reads thecorrection data corresponding to the temperature from the gammacorrection table. The control circuit 32 carries out gamma correction onthe display data according to the correction data and adjusts a writevoltage to each of the liquid crystal cells C.

The temperature of the liquid crystal panel A may be detected by atemperature sensor or by monitoring a value of an electric currentflowing in elements such as the TFTs.

In this embodiment, the same effect as by the first and thirdembodiments can be obtained. Furthermore, in this embodiment, a stillimage is displayed according to the hold driving and a moving image isdisplayed according to the impulse driving. Therefore, optimal screendisplay can be realized for any image.

Since the brightness of the fluorescent tubes F1–F4 is increased at thetime of the impulse driving, variance between the impulse driving andthe hold driving can be reduced.

Since optimal gamma correction is carried out in the hold driving and inthe impulse driving, a change in the amount of light penetrating throughthe liquid crystal cells C can be faster especially in the impulsedriving. Therefore, brightness can be increased.

Since the gamma correction is carried out in response to the temperaturechange of the liquid crystal panel A, brightness, contrast, andgray-scale displaying characteristics can be constant regardless of thetemperature change in the liquid crystal panel A.

The Seventh Embodiment of the Liquid Crystal Display Device and theSeventh Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 22 shows an outline of the liquid crystal panel A of the TFT (ThinFilm Transistor) driving liquid crystal display device used in thisembodiment.

The liquid crystal panel A comprises the four first pixel regions 20 andthe four second pixel regions 22 arranged alternately in the form ofstripes. The first pixel regions 20 and the second pixel regions 22 aredivided corresponding to the liquid crystal cells C for one line. Theliquid crystal panel A is assumed to have 8 pixels in vertical directionand 8 pixels in horizontal direction, for the sake of simplerexplanation. Other configurations are the same as in the firstembodiment described above. In FIG. 22, numbers in parentheses showntogether with the scanning lines G1–G8 indicate a driving order of thescanning lines G1–G8.

FIG. 23 shows timings at which display data are written in the liquidcrystal display device.

A control circuit which is not shown activates the scanning lines G1,G8, G3, G6, G2, G4, G5 and G7 in this order in the first filed and inthe second field. In the first filed, the control circuit writes in thefirst pixel regions 20 data corresponding thereto out of the displaydata, and writes black data in the second pixel regions 22. In thesecond field, the control circuit writes in the second pixel regions 22data corresponding thereto out of the display data, and writes blackdata in the first pixel regions 20.

In this embodiment, the same effect as by the first embodiment can beobtained. Furthermore, in this embodiment, the scanning lines G1–G8 aredriven in the predetermined order which is not related to an order thescanning lines are arranged in. Therefore, flicker is prevented withmore certainty.

The Eighth Embodiment of the Liquid Crystal Display Device and theEighth Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 24 shows an outline of the liquid crystal panel A of the TFT (ThinFilm Transistor) driving liquid crystal display device used in thisembodiment. In this embodiment, elements corresponding to the elementsdescribed above for the first embodiment are given the same referencenumerals and explanation of these elements is not repeated.

The liquid crystal panel A comprises the two first pixel regions 20 andthe two second pixel regions 22 arranged alternately in a stripe-likepattern. Each of the first pixel regions 20 and the second pixel regions22 is divided according to the liquid crystal cells C for 3 lines. Theliquid crystal panel A is assumed to have 12 pixels in the verticaldirection and 8 pixels in the horizontal direction, for the sake ofsimpler explanation. Other configurations are the same as in the firstembodiment described above. In FIG. 24, numbers in parentheses showntogether with the scanning lines G1–G12 indicate a driving order of thescanning lines G1–G12.

FIG. 25 shows timings at which display data are written in the liquidcrystal display device.

A control circuit which is not shown activates the scanning lines G1,G7, G4, G10, G2, G8, G5, G11, G3, G9, G6 and G12 in this order in thefirst filed and in the second field. In the first filed, the controlcircuit writes in the first pixel regions 20 data corresponding theretoout of the display data, and writes black data in the second pixelregions 22. In the second field, the control circuit writes in thesecond pixel regions 22 data corresponding thereto out of the displaydata, and writes black data in the first pixel regions 20.

In this embodiment, the same effect as by the first embodiment and bythe seventh embodiment can be obtained. Furthermore, in this embodiment,line-sequential scanning is carried out in a portion of the areas.Therefore, flicker is prevented with more certainty, without causing astructure of the control circuit to become complex.

The Ninth Embodiment of the Liquid Crystal Display Device

FIG. 26 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

In this embodiment, the liquid crystal panel A comprises a plurality ofthe liquid crystal cells C arranged vertically and horizontally. On thebackside of the liquid crystal panel A, the fluorescent tubes F1–F4 arearranged corresponding to band-like areas Gr.1, Gr.2, Gr.3, and Gr.4each formed by the liquid crystal cells C over a plurality of lines.Each of the fluorescent tubes F1–F4 may be formed with a plurality offluorescent tubes. A control circuit 40 has a function of carrying outon-off control of pairs of the fluorescent tubes F1 and F3, and F2 andF4, in which the fluorescent tubes are not adjacent to each other. Thecontrol circuit 40 also has a function of carrying out hold driving. Thefluorescent tubes F1 and F3 are turned on and off as first backlightsand the fluorescent tubes F2 and F4 are turned on and off as secondbacklights.

FIG. 27 shows timings at which display data are written in the liquidcrystal display device. For simpler explanation, an example of theliquid crystal panel A comprising 12 scanning lines G1–G12 is shown.

The control circuit 40 carries out hold driving in which the scanninglines G1–G3 and G7–G9 are scanned sequentially in the first field, andthe scanning lines G4–G6 and G10–G12 are sequentially scanned in thesecond field. Each of the scanning lines G1–G12 is activated once in oneframe period.

The control circuit 40 turns on the fluorescent tubes F1 and F3 andturns off the fluorescent tubes F2 and F4 in the first field. In thesecond field, the control circuit turns on the fluorescent tubes F2 andF4 and turns off the fluorescent tubes F1 and F3. As a result, in thefirst field, pixels corresponding to the fluorescent tubes F1 and F3 aredisplayed, and pixels corresponding to the fluorescent tubes F2 and F4are displayed in the second field. In other words, the fluorescent tubesF1 and F3 and the fluorescent tubes F2 and F4 are turned on and offalternately and pseudo-impulse driving is carried out.

In this embodiment, the same effects as by the first embodimentdescribed above can be obtained.

The Tenth Embodiment of the Liquid Crystal Display Device

FIG. 28 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe above embodiments are given the same reference numerals andexplanation of these elements is not repeated.

In this embodiment, the liquid crystal display device comprises theliquid crystal panel A, the fluorescent tubes F1–F4, the Y driver 14,and the X driver 16 which are the same as in the ninth embodiment above.On the backside of the liquid crystal panel A, the fluorescent tubesF1–F4 are arranged corresponding to the band-like areas Gr.1, Gr.2,Gr.3, and Gr.4 divided into a plurality of the liquid crystal cells Cover a plurality of the lines.

A control circuit 41 has a function of sequentially turning on and offthe fluorescent tubes F1–F4. The control circuit 41 may turn on and offtwo or more areas at the same time. In this embodiment, the liquidcrystal panel A is divided into the large areas Gr.1, Gr.2, Gr.3, andGr.4. However, the panel A can be divided into two or any larger numberof groups.

FIG. 29 shows timings at which display data are written in the liquidcrystal display device described above (including on and off timings ofthe fluorescent tubes F1–F4). For simpler explanation, an example of theliquid crystal panel A comprising the 12 scanning lines G1–G12 is shown.

A period of turning on and off each of the fluorescent tubes F1–F4 is inagreement with the period of one frame, that is, in agreement with ascanning period of the liquid crystal panel A. The area Gr.1 is formedby three small groups comprising pixels on the lines of the scanninglines G1–G3. Likewise, the areas Gr.2, Gr.3, and Gr.4 comprise threegroups each.

Hereinafter, an operation mainly in the area Gr.1 will be explained.

The control circuit 41 writes display data in the scanning lines G1–G3and then turns on the fluorescent tube F1 corresponding to the area Gr.1after a predetermined time T1 has elapsed. The control circuit 41 turnsoff the fluorescent tube F1 at a timing which is a predetermined time T2before the scanning line G1 is scanned. The predetermined times T can be“0”. However, it is preferable for the times T to be set more than atime necessary for turning off the fluorescent tube F1. In this manner,displaying two images at one time can be prevented. By setting the timeT1 more than ½ of the one frame period (16 ms, in this case), durationof displaying black becomes longer and more preferable display can berealized.

It is preferable for liquid crystal elements on the scanning line G3scanned last in the area Gr. 1 to have completed responding before thefluorescent tube F1 is turned on. For this reason, it is preferable forthe response time in all gradations of the liquid crystal elements to beshorter than the predetermined time T1. For example, π cells or a liquidcrystal display device of an in-plane switching mode having vertical orhorizontal alignment are preferably used. The predetermined time T1 ispreferably set to be equal to or shorter than ⅘ of one frame period.Since one frame period is generally 16 ms, it is preferable for theresponse speed of the liquid crystals to be adjusted to 10 ms or smallerfor all gradations.

The control circuit 41 carries out the same control for the areas Gr.2,Gr.3 and Gr.4.

In this embodiment, the same effect as by the first embodiment describedabove can be obtained.

The Ninth Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 30 shows a liquid crystal display device 42 and a personal computer44 used in this embodiment.

The liquid crystal display device 42 has the same configuration as theliquid crystal display device having been used conventionally. Theliquid crystal display device 42 comprises a control circuit 46, an Xdriver, a Y driver, and the liquid crystal panel A. The control circuit46 has an A/D conversion unit 48.

The personal computer 44 comprises a video card 50 for convertingdigital display data into analog data. The video card 50 has a functionof converting display data for one frame into black data in every otherline, upon conversion to analog data. Therefore, black data are writtenin every other line. The display data converted to the black data can bedeleted or used for display in a subsequent frame. The video card 50sequentially sends to the A/D conversion unit 48 of the liquid crystaldisplay device 42 the display data in which the black data are includedin every other line.

The liquid crystal display device 42 displays the data having beenreceived on the liquid crystal panel A as they are. The black data aredisplayed in stripes in every other line on the liquid crystal panel A.

In this embodiment, blurring in an image and flicker can be preventedeven if the liquid crystal display device 42 which is the same as theconventional device is used.

In this embodiment, the video card 50 has the function of conversion toblack data. However, the present invention is not limited to thisexample. The A/D conversion unit 48 in the liquid crystal display device42 may have the conversion function to the black data, for example.

The Tenth Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 31 shows a personal computer 52 used in this embodiment. Thepersonal computer 52 comprises a built-in liquid crystal display device54, such as in the case of a notebook type computer. The computer 52 hasa conversion unit 58 for converting a portion of digital display datainto black data.

The data conversion unit 58 has the function of converting the displaydata for one frame into black data in every other line. Therefore, blackdata are written in every other line. The display data converted to theblack data may be deleted or used for display in a subsequent frame. Thedata conversion unit 58 sequentially sends to a control circuit 56 ofthe liquid crystal display device 54 the display data in which the blackdata are included in every other line. The liquid crystal display device54 displays the data having been received on the liquid crystal panel Aas they are. The black data forming stripes are displayed on the liquidcrystal panel A in every other line. The data conversion unit 58 may beformed with an electronic circuit or by using a software program.

In this embodiment, the same effect as by the tenth embodiment of theliquid crystal display device controlling method can be obtained.

In this embodiment, an example of the data conversion unit 58 having theconversion function to the black data has been explained. However, thepresent invention is not limited to this example. The control circuit 56of the liquid crystal display device 54 may have the conversionfunction, for example.

The Eleventh Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 32 shows an outline of a liquid crystal display device 60 used inthis embodiment.

A control circuit 62 of the liquid crystal display device 60 has a dataconversion unit 64 for converting display data of an interlace method(TV signals) supplied from exterior. The liquid crystal display device60 also comprises the conventional X driver, the Y driver, and theliquid crystal panel A.

The data conversion unit 64 has functions of receiving display dataA1–A4 and B1–B4 of respective fields, shown as in FIG. 32, and insertingblack data into these display data. The control circuit displays on theliquid crystal panel A the data of each field having the black datainserted therein as display data in one frame. A screen is displayed onthe liquid crystal panel A, in which black data forming stripes aredisplayed in every other line.

In this embodiment, the same effect as by the tenth embodiment of theliquid crystal display device controlling method can be obtained.Furthermore, in this embodiment, a preferable screen not having blurringin an image can be configured by using the display data of the interlacemethod (TV signals).

In the above embodiments, the time in which the display data are writtenand the time in which the black data are written are the same, as shownby the waveforms in FIG. 10. However, the present invention is notlimited to this example, and the time of writing the display data may beshorter than the time of writing the black data. In this case, blurringin an image can be reduced further.

In the above embodiments, one frame period is set to 16 ms. However, thepresent invention is not limited to this example, and one frame periodis determined according to the response time of the cells used.

The Eleventh Embodiment of the Liquid Crystal Display Device

FIG. 33 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

This liquid crystal display device comprises TFTs and pixel electrodes12 both laid out in the form of a matrix. Gate electrodes of the TFTswhich are switching elements are connected to the scanning lines G1, G2,. . . , Gn. The scanning lines G1, G2, . . . , Gn are signal lines fortransmitting gate signals output from the Y driver 14. Drain electrodesof the TFTs (Thin Film Transistors) are connected to the signal linesD1, D2, . . . , Dm. The signal lines D1, D2, . . . , Gm are signal linesfor transmitting data signals output from the X driver 16. Sourceelectrodes of the TFTs are respectively connected to the pixelelectrodes 12.

Counter electrodes (not shown) are arranged, facing the pixel electrodes12. Liquid crystals (not shown) are sandwiched between the pixelelectrodes 12 and the counter electrodes, and the liquid crystal cells Care formed. The liquid crystal panel A is formed with the liquid crystalcells C arranged vertically and horizontally.

The liquid crystal panel A is divided into 5 pixel regions 70 along thescanning lines. On the backside of the liquid crystal panel A, atransparent light guide plate 72 formed with an acrylic resin or thelike is arranged facing the liquid crystal panel A. A fluorescent tube(cold cathode tube) F5 is arranged as a backlight at one end of thedirection of the scanning line Gn on the light guide plate 72.

In this embodiment, a 15-inch XGA liquid crystal panel is used as theliquid crystal panel A. The liquid crystal panel A adopts an improved VA(Vertical Alignment) type or an OCB (Optically CompensatedBirefringence) type. A response time of the liquid crystal panel A is 7ms, which is fast.

FIG. 34 shows the backlight in detail.

A liquid crystal film 74 of polymer-diffused type is bonded on the lightguide plate 72, on the opposite side of the liquid crystal panel A. Inthis embodiment, an LC light modulation sheet “Um film” manufactured byNippon Sheet Glass is used as the liquid crystal film. Counterelectrodes (not shown) of the liquid crystal film 74 are divided into 5areas along the direction of guiding the light emitted by thefluorescent tube F5, and 5 scattering parts 74 a˜74 e are formed. InFIG. 34, for the sake of simpler explanation, the liquid crystal film 74is divided into 5 areas. In reality, the liquid crystal film 74 itselfis formed with one sheet. Positions at which the parts 74 a˜74 e areformed correspond to the 5 pixel regions 70 of the liquid crystal panelA.

A scattering sheet 76 such as a prism sheet for scattering the lightfrom the light guide plate 72 is bonded on the light guide plate 72, onthe side of the liquid crystal panel A. A mirror 78 for reflecting thelight toward the light guide plate 72 is bonded on the outer surface ofthe liquid crystal film 74.

For bonding the materials, emulsion oil having almost the samerefractive index as the acrylic board is used.

In the example shown in FIG. 34, a voltage is not supplied to thecounter electrode of the scattering part 74 d shown by a hatched area.The scattering part 74 a becomes a scattering part scattering light. Apredetermined voltage is supplied to the counter electrodes of theremaining scattering parts 74 a, 74 b, 74 c, and 74 e. These scatteringparts transmit the light. As a result, the light is emitted only on thepixel region 70 of the liquid crystal panel A facing the scattering part74 d. The scattering parts can be formed and disappear easily bycontrolling the counter electrodes of the scattering parts 74 a˜74 e.

By using a mirror or the like for reflecting light on both ends (rightand left of FIG. 34) of the light guide plate 72, the light propagatesthrough the light guide plate 72 repeatedly and is scattered by thescattering part 74 d to be guided to exterior of the light guide plate72, which is not shown. In other words, the light from the fluorescenttube F5 is collected at a desired position and emitted.

As has been described above, the light emitted on the light guide plate72 can be used efficiently according to this embodiment, and powerconsumption can be reduced. In this example, power consumption of thefluorescent tube F5 can be reduced up to 1/5. Furthermore, since theluminescent parts can be solely formed with the fluorescent tube F5,uneven display due to degradation of the fluorescent tube does notoccur. The liquid crystal film 74 is bonded on the light guide plate 72on the opposite side of the liquid crystal panel A. Therefore, the lightemitted toward the liquid crystal panel A is not shut by the liquidcrystal film 74. Since the scattering parts are not in contact with theliquid crystal panel A, a boundary between neighboring luminescent partscan become inconspicuous. The scattering parts can be formed easily bythe liquid crystal film 74 of the high-molecular type.

FIG. 35 shows control of the liquid crystal panel A and the backlight ofthe liquid crystal display device described above. The verticaldirection of FIG. 35 represents time and the horizontal directionthereof shows the direction of guiding the light from the fluorescenttube F5. Arrows shown in FIG. 35 indicate scan of the scanning lines.

In this embodiment, line-sequential scanning by hold driving, in whichthe scanning lines are scanned once in one frame period and display dataare written in the pixel electrodes 12, is carried out. The scanninglines are sequentially scanned toward lower right of FIG. 35. Thebacklight is turned on for 3.2 ms after one pixel region 70 is scanned.This duration, 3.2 ms, is ⅕ of one frame period (16 ms) and equal to thescanning period of one of the pixel regions 70. The phrase stating that“the backlight is turned on” refers to a shift to a state in which thescattering parts 74 a˜74 e of the liquid crystal film 74 scatter thelight.

For example, in the pixel regions 70 corresponding to the scatteringpart 74 d, the time between scan of the last scanning line Gn and thebacklight′ becoming on is 9.6 ms. This time shows a worst response timeof the liquid crystal cells C shown in FIG. 33, and expressed by thefollowing equation (1) with n being the number of the pixel regions 70:1 frame period×(n−2)/n  (1)

Since the response speed of the liquid crystals in this embodiment isapproximately 7 ms, the cell C in which the display data are written ata last scan of the pixel regions 70 can complete responding withcertainty, before the backlight is turned on. As a result, even in thecase of displaying a moving image, occurrence of blurring is alleviated.

In FIG. 34, the scattering parts 74 a˜74 e are bonded on the light guideplate 72 on the opposite side of the liquid crystal panel A. However,the scattering parts 74 a˜74 e may be bonded on the light guide plate 72on the side of the liquid crystal panel A. In this case, the lightirregularly reflected by the scattering parts 74 a˜74 e is emitted toexterior of the light guide plate 72, and emitted to a predeterminedluminescent part of the liquid crystal panel A. Since a boundary betweenneighboring luminescent parts becomes clearer, impulse driving can becarried out with good visibility, and flicker is prevented.

The Twelfth Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display device inthis embodiment are the same as in FIG. 33, except for the liquidcrystal cells C comprising π cells in this embodiment. The response timeof the π cells is fast, approximately 2 ms.

FIG. 36 shows the backlight used in this embodiment in detail.

In this embodiment, the liquid crystal film 74 the same as in FIG. 34 issandwiched between two light guide plates 80. Therefore, the liquidcrystal film 74 is securely protected by the light guide plates 80.Furthermore, due to a so-called sandwich structure, this light emissionsystem can be formed easily with accuracy. FIG. 36 shows that thescattering part 74 d shown by a stippled area is a scattering area forscattering light.

The scattering plate 76 such as a prism for scattering light from thelight guide plates 80 is bonded on one of the light guide plates 80, onthe side of the liquid crystal panel A. The mirror 78 for reflectinglight toward the light guide plates 80 is bonded on the other lightguide plate 80, on the opposite side of the liquid crystal panel A.

FIG. 37 shows control of the liquid crystal panel A and the backlight inthe liquid crystal display device described above.

In FIG. 37, the vertical direction shows time and the horizontaldirection shows a direction of guiding the light emitted from thefluorescent tube F5.

In this embodiment, line-sequential scanning by impulse driving, inwhich each of the scanning lines is scanned twice in one frame periodand reset data (black) and display data are written in the pixelelectrodes 12, is carried out. The scanning lines are sequentiallyscanned toward lower right of FIG. 35. Gray arrows show scan of thescanning lines for writing the reset data while black arrows show scanof the scanning lines for writing the display data.

The backlight is turned on for 3.2 ms after the predetermined pixelregion 70 is scanned. This duration, 3.2 ms, is 1/5 of one frame period(16 ms) and equal to the scanning period of one of the pixel regions 70.The display data are written 6.4 ms after the reset data have beenwritten.

For example, in the pixel regions 70 corresponding to the scatteringpart 74 d, the time between scan of the last scanning line Gn and thebacklight's becoming on is 3.2 ms. This time shows a worst response timeof the liquid crystal cells C, and expressed by the following equation(2) with n being the number of the pixel regions 70:One-frame period×[[(n−1)/(2×n)]˜1/n]  (2)

Since the response time of the liquid crystals in this embodiment isapproximately 2 ms, the cell C in which the display data are written ata last scan of the pixel regions 70 can complete responding withcertainty, before the backlight is turned on. As a result, even in thecase of displaying a moving image, occurrence of blurring is alleviated.

In the case where the number of the pixel regions 70 is even, the worstresponse time of the liquid crystals is expressed by the followingequation (3):One-frame period×[[(n−2)/(2×n)]−1/n]  (3)

For example, in the case of the liquid crystal panel A having six pixelregions 70, preferable screen display can be realized by using theliquid crystal cells C having the response time approximately equal toor smaller than approximately 2.6 ms.

In this embodiment, the same effect as by the embodiment shown in FIG.33 can be obtained. Furthermore, in this embodiment, the liquid crystalfilm 74 can be protected securely by being sandwiched between the lightguide plates 80. Moreover, the light emission system comprising thelight guide plates 80 and the scattering parts 74 a˜74 e can be formedeasily with accuracy.

The liquid crystal film 74 may not only be sandwiched between the lightguide plates 80 but also further be bonded on the outer surfaces of thelight guide plates 80 as shown in FIG. 38.

The Thirteenth Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display deviceare the same as in FIG. 33.

FIG. 39 shows a backlight used in this embodiment in detail.

In this embodiment, the light guide plate 82 is divided into 5 portionsalong the direction of guiding the light from the fluorescent tube F5.Scattering parts 84 a˜84 d comprising a film 84 of high-molecular typeare bonded on 4 partitions of the light guide plate 82. The partitionsof the light guide plate 82 are orthogonal to the direction light isguided. A scattering portion 84 e comprising the liquid crystal film 84is bonded on one partition of the light guide plate 82 arranged on theside of the fluorescent tube F5. The scattering parts 84 a˜84 e arearranged orthogonal to the direction light is guided, cutting across thedirection. In other words, the light penetrating through the light guideplate 82 always penetrates through the scattering parts 84 a˜84 e.

FIG. 40 shows a detailed structure of the liquid crystal film 84.

The liquid crystal film 84 has a structure in which nematic liquidcrystals 85 a (low molecular liquid crystal) having negative isotropy ofdielectric constant E are covered with a resin layer 85 b. The resinlayer 85 b is formed with high-molecular liquid crystal. In thisembodiment, a UV curable liquid crystal resin manufactured by DainipponInk & Chemicals Inc. is used for the resin layer 85 b. In the liquidcrystals 85 a and the resin layer 85 b, a refractive index n1 of theliquid crystals in the radial direction is the same as a refractiveindex n2 of the liquid crystals in the axial direction.

All liquid crystals in the liquid crystal film 84 are aligned orthogonalto a surface of the liquid crystal film 84 in a state in which a voltageis not supplied to the counter electrodes, and let the incident lightpenetrate through. When the voltage is supplied to the counterelectrodes, the nematic liquid crystals 85 a of the liquid crystal film84 try to become orthogonal to an electric field. The axial direction ofthe liquid crystals 85 a becomes random, and incident light isscattered. The voltage is applied to the scattering part 84 d shown by astippled area in FIG. 39, and the part becomes a scattering areascattering light.

The liquid crystal film 84 is manufactured by injecting a mixture of theUV curable liquid crystals and low molecular liquid crystals after asubstrate is coated with a vertical-alignment film, and by hardening theresin layer 85 b with ultraviolet rays.

FIG. 41 shows an example of the liquid crystal film formed with anordinary resin layer (high polymer).

The liquid crystal film of this kind has different refractive indicesbetween the liquid crystal layer and the resin layer. Therefore, lightentering obliquely is scattered by the liquid crystal film. The liquidcrystal film 84 shown in FIG. 40 lets the light entering obliquelypenetrate through.

In this embodiment, the same effect as by the embodiment shown in FIG.36 can be obtained. Furthermore, in this embodiment, the lightpenetrating through the light guide plate 82 always penetrates throughany one of the scattering parts 84 a˜84 e. Therefore, the light can bescattered with certainty.

The scattering parts 84 a˜84 e are orthogonal to the direction light isguided. Therefore, the partitions of the light guide plate 82 need to besimply vertical and the scattering parts 84˜84 e are jointed easily withthe light guide plate 82 with accuracy.

The resin layer 85 b covering the nematic liquid crystals 85 a in theliquid crystal film 84 are formed with the high-molecular liquidcrystals having the same refractive index as the nematic liquid crystals85 a. Therefore, in a state where the scattering parts let the lightpenetrate, the light is prevented from being scattered at an interfacebetween the nematic liquid crystals 85 a and the resin layer 85 b.

If the nematic liquid crystals 85 a and the high-molecular liquidcrystals are aligned orthogonal to the direction light is guided in astate where the voltage is not applied to the counter electrodes, thesame effect can be obtained.

The Fourteenth Embodiment of the Liquid Crystal Display Device

Configurations of the main portions of the liquid crystal display deviceare the same as in FIG. 33.

FIG. 42 shows the backlight used in this embodiment in detail.

In this embodiment, the scattering parts 84 a˜85 e are arrangedobliquely along the direction of guiding the light from the fluorescenttube F5. Other configurations are the same as in FIG. 38.

In this embodiment, light penetrating through the inside of light guideplate 86 is necessarily scattered by the scattering parts 84 a˜84 e, andthe scattered light can be emitted in a large dose toward the liquidcrystal panel A.

The Fifteenth Embodiment of the Liquid Crystal Display Device and theTwelfth Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 43 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe above embodiment are given the same reference numerals andexplanation of these elements is not repeated.

In this embodiment, the liquid crystal panel A is formed with the liquidcrystal cells C arranged vertically and horizontally. A backlight 88comprising the light guide plate 72, the liquid crystal film 74, and thefluorescent tube F5 is arranged on the backside of the liquid crystalpanel A. A control circuit 90 receives an output from a manual switch SWand display data, and controls the Y driver 14, the X driver 16, and thebacklight 88.

The manual switch SW is a switch for adjusting a luminescent periodbetween the display data writing and the reset data writing. In otherwords, a viewer of a display screen of the liquid crystal panel A canfreely adjust the luminescent period.

The control circuit 90 carries out line-sequential scanning according toimpulse driving in which each of the scanning lines is scanned twice inone frame period, and the display data and the reset data (black) arewritten in the liquid crystal cells C. The control circuit 90 controlsthe backlight 88 and causes the scattering parts 74 a˜74 e formed on thelight guide plate 72 to sequentially emit light, in synchronization withdisplay data writing. In other words, the luminescent period is adjustedby the impulse driving of the liquid crystal panel A and the control ofthe backlight.

The control circuit 90 adjusts the luminous intensity of the fluorescenttube F5 in response to the operation of the manual switch SW, so thatthe display brightness is kept constant.

In this embodiment, the viewer of the display screen can directly adjustthe display screen for optimal view, by controlling the manual switchSW. For example, the luminescent period is increased when a still imageis being viewed, while the time is shortened when a moving image isbeing viewed. In this manner, the display screen can be adjusted inaccordance with a sense of the viewer. Therefore, blurring in a movingimage is alleviated and flicker is prevented.

The display brightness of the liquid crystal panel A is controlled to beconstant, in relation to the luminescent period control. Regardless ofthe image being still or moving, the display brightness can be keptconstant and the screen becomes easier to see.

The luminescent period may be adjusted by arranging a shutter comprisinga liquid crystals or the like on a front surface of the liquid crystalpanel A and by controlling the liquid crystal shutter.

Furthermore, the brightness control of the display screen can be carriedout according to the amount of the display data to be written in theliquid crystal cells C.

The Sixteenth Embodiment of the Liquid Crystal Display Device and theThirteenth Embodiment of the Liquid Crystal Display Device ControllingMethod

FIG. 44 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe above embodiment are given the same reference numerals andexplanation of these elements is not repeated.

In this embodiment, as in the above embodiment, the luminescent periodis controlled by the impulse driving of the liquid crystal panel A andthe backlight control.

A control circuit 92 receives information from a DCT (Discrete CosineTransform) unit 94 for estimating motion of display data and judgeswhether the display data are of a still image or a moving image. Thecontrol circuit 92 controls the luminescent period in accordance withthe display image. More specifically, the control circuit 92 judges animage to be moving when estimate of the motion of a DC component in theDCT exceeds the size of one block (16 pixels×16 lines). In the case ofthe moving image, the luminescent period is shortened, and thebrightness of the backlight 88 is increased. The display brightness ofthe liquid crystal panel A is kept constant.

By using the information of DCT, consecutive still images are preventedfrom being judged moving due to a fluctuation of analog signals.Especially, it is preferable for an image to be judged as moving whenthe DC component changes by 10% or more.

In this embodiment, the luminescent period is adjusted by judging thedisplay data to represent a still image or a moving image, using theinformation of DCT. By shortening the luminescent period for movingimage display, blurring in the image is alleviated and flicker isprevented.

By using DCT widely used in motion compensation of moving images, theimages can be judged still or moving with certainty.

The luminescent period can be adjusted by arranging a shutter comprisingliquid crystals or the like on a front surface of the liquid crystalpanel A, and by controlling the liquid crystal shutter.

The Seventeenth Embodiment of the Liquid Crystal Display Device

FIG. 45A shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment. In thisembodiment, elements corresponding to the elements described above forthe above embodiment are given the same reference numerals andexplanation of these elements is not repeated.

Configurations of a main portion of the liquid crystal display deviceare the same as in FIG. 44.

A control circuit 96 has a function of switching from impulse driving tohold driving and vice versa. The control circuit 96 carries out the holddriving in the case of display data for a still image and the impulsedriving in the case of a moving image. The control circuit 96 carriesout the impulse driving by impulse control of the scanning lines Gn andthe on-off control of the backlight.

The display image is judged to be moving when a ratio of differencebetween pixels in a display image in one frame and pixels in a displayimage in an immediately preceding frame exceeds 10%. In other words, ifthe ratio of moving image to display data exceeds a predetermined value,the control is switched from the hold driving to the impulse driving.

Furthermore, the control circuit 96 increases the brightness of thebacklight 88 when a moving image is displayed, and causes the displaybrightness of the liquid crystal panel A to be equal to the brightnessin the case of a still image. Therefore, regardless of whether the holddriving or the impulse driving is carried out, the display brightness ofthe liquid crystal panel A becomes constant. In other words, the displaybrightness can be reduced at the time of still image display and powerconsumption can be reduced.

In this embodiment, polysilicon TFTs are used as the switching elements.Since the pixel electrodes are controlled by the polysilicon TFTs havinga faster switching speed than amorphous silicon TFTS, blurring in amoving image can be alleviated, especially in the case of the impulsedriving.

In this embodiment, blurring in a moving image can also be alleviatedand flicker is prevented.

The present invention is not limited to the above embodiment. Thedisplay image may be judged to be moving when the display data changesfor two or more frames, and the hold driving is then switched to theimpulse driving.

Furthermore, the display image may be judged to be moving when motioncompensation is carried out according to DCT (Discrete Cosine Transform)and vector information indicating motion of an image is included incompressed image information. The hold driving is then switched to theimpulse driving.

Moreover, as shown in FIG. 45B, a shutter comprising liquid crystals orthe like may be arranged on a front surface of the liquid crystal panelA so that the luminescent period in the impulse driving can be adjustedby controlling the liquid crystal shutter. (The eighteenth embodiment ofthe liquid crystal display device).

Configurations of a main portion of the liquid crystal display deviceare the same as in FIG. 33. In this embodiment, elements correspondingto the elements described above for FIG. 33 are given the same referencenumerals and explanation of these elements is not repeated.

FIG. 46 shows the backlight unit BLU used in this embodiment in detail.

The backlight unit BLU has a light guide plate 102. A polarizationsplitting sheet 104 a (a first polarization splitting sheet), a liquidcrystal shutter 106, a polarization splitting sheet 104 b (a secondpolarization splitting sheet), and a scattering sheet 108 are bonded inthis order on the light guide plate 102, on the opposite side of theliquid crystal panel A. The polarization splitting sheets 104 a and 104b let a normal light component out of unpolarized light penetrate andreflect a component other than the normal light component (an abnormallight components).

In this embodiment, an acrylic board (refractive index: approximately1.5) is used for the light guide plate 102 and “Transmax” of MercK JapanLtd. is used for the polarization splitting sheets 104 a and 104 b.“Transmax” is formed with cholesteric liquid crystals. The liquidcrystal shutter 106 is divided into 10 areas (only 3 areas are shown inFIG. 46) along the scanning lines. The liquid crystal shutter 106 has afunction of sequentially opening (a penetrative state) each of the areasin accordance with the impulse control of the liquid crystal panel A.The refractive indices of “Transmax” and the liquid crystal shutter 106are approximately 1.5, which is the same as the refractive index of thelight guide plate 102. The scattering sheet 108 is formed with a resinboard of milk white color. A 15-inch XGA liquid crystal panel is used asthe liquid crystal panel A.

An operation of the backlight unit BLU will be explained next.

Light emitted from the fluorescent tube F5 (unpolarized light)propagates while being totally reflected (ranging 0˜4.) within the lightguide plate 102. The abnormal light component is reflected by thepolarization splitting sheet 104 a and propagates within the light guideplate 102 while being totally reflected [FIG. 46( a)]. The normal lightcomponent penetrates through the polarization splitting sheet 104 a andreaches the liquid crystal shutter 106. In the case where the liquidcrystal shutter 106 is in a state of birefringence (portions shown bystippled areas), the component having penetrated through thepolarization splitting sheet 104 a is subjected to the phase shift by 90by the liquid crystal shutter 106, and reaches the polarizationsplitting sheet 104 b as an abnormal light component [FIG. 46( b)]. Thelight is reflected by the polarization splitting sheet 104 b again andsubjected to the phase shift by 90. by the liquid crystal shutter 106 tobecome the original normal light component. Thereafter, the lightpenetrates through the polarization splitting sheet 104 a and isreturned to within the light guide plate 102 [FIG. 46( c)]. On the otherhand, in the case where the liquid crystal shutter 106 is not in thestate of birefringence (shown by a white portion in FIG. 46), the lighthaving penetrated through the polarization splitting sheet 104 a(thenormal light component) penetrates through the liquid crystal shutter106 and the polarization splitting sheet 104 b, and is scattered(reflected) by the scattering sheet 108 [FIG. 46( d)]. The lightirregularly reflected by the scattering sheet 108 penetrates through thepolarization splitting sheet 104 b, the liquid crystal shutter 106, andthe polarization splitting sheet 104 a and returns to the light guideplate 102. At this time, most components of the light exceeds a criticalangle and emitted to the liquid crystal panel A, penetrating through thelight guide plate 102 [FIG. 46( e)].

The liquid crystal display device can easily carry out the impulsedriving by causing the predetermined area of the liquid crystal shutterto sequentially become penetrative in accordance with control of thepanel. Therefore, blurring in a moving image can be alleviated andflicker is prevented.

Although not shown, the light can repeatedly penetrate through the lightguide plate 102 if mirrors or the like for reflecting the light are setat both ends (right and left) of the light guide plate 102. The light isthen emitted from the predetermined area of the liquid crystal shutter106 to the liquid crystal panel A. In other words, the light emittedfrom the fluorescent tube F5 is collected at a desired position andemitted therefrom.

As has been described above, in this embodiment, the light emitted tothe light guide plate 102 can be used efficiently and power consumptioncan thereby be reduced. In this example, the power consumption of thefluorescent tube F5 can be reduced up to 1/10. Furthermore, since theplurality of the luminescent parts can be formed by using thefluorescent tube F5 alone, uneven display caused by degradation of thefluorescent tube does not occur.

The Nineteenth Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display deviceare the same as those of the eighteenth embodiment. In this embodiment,elements corresponding to the elements described above for theeighteenth embodiment are given the same reference numerals andexplanation of these elements is not repeated.

FIG. 47 shows the backlight unit BLU used in this embodiment in detail.

In this embodiment, a retardation sheet 110 having 100 nm retardation ispasted on the light guide plate 102, on the side of the back liquidcrystal panel A. The retardation value of the retardation sheet 110 isnot specifically limited. Configurations other than the above are thesame as in FIG. 46.

FIG. 48 shows a retardation axis A1 of the retardation sheet 110, atransmissive axis A2 of the polarization splitting sheet 104 a, a liquidcrystal alignment direction A3 of the liquid crystal shutter 106, and atransmissive axis of the polarization splitting sheet 104 b. In thisembodiment, the directions of the transmissive axes A2 and A4 are set tobe in accordance with the liquid crystal alignment direction A3. Thedirection of the retardation axis A1 can be arbitrary.

As shown in FIG. 47, light penetrating through the light guide plate 102is subjected to phase shift of reflected light by the retardation sheet110. In other words, the phase of the light totally reflected within thelight guide plate 102 (the abnormal light component) is shifted by theretardation sheet 110 and becomes to include the normal light component.Consequently, the normal light component penetrating through thepolarization splitting sheet 104 a can be increased.

In this embodiment, the same effect as by the eighteenth embodiment canbe obtained. Furthermore, in this embodiment, the light can be usedefficiently and power consumption is thus reduced more.

The Twentieth Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of this device are the same as theeighteenth embodiment. In this embodiment, elements corresponding to theelements described above for the eighteenth embodiment are given thesame reference numerals and explanation of these elements is notrepeated.

FIG. 49 shows the backlight unit BLU used in this embodiment in detail.

In this embodiment, instead of the scattering sheet 108, a prism sheet112 comprising a plurality of prisms 112 a is bonded. Configurationsother than the prism sheet are the same as in FIG. 46.

A prism surface of each of the prisms 112 a comprises a reflection film112 b on which aluminum or the like is vapor-deposited. Each of theprisms 112 a is designed to reflect incident light to a directionforming an angle of ±20° with a direction orthogonal to the liquidcrystal panel A. In other words, the normal light component penetratingthrough the liquid crystal shutter 106 is reflected by the prism sheet112 and emitted toward the liquid crystal panel A in a direction almostorthogonal to the liquid crystal panel A.

In this embodiment, the same effect as by the eighteenth embodiment canbe obtained. Furthermore, in this embodiment, the light is emitted atthe predetermined angle toward the liquid crystal panel A and luminousintensity can be improved.

The Twenty-First Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display deviceare the same as those of the eighteenth embodiment. In this embodiment,elements corresponding to the elements described above for theeighteenth embodiment are given the same reference numerals andexplanation of these elements is not repeated.

FIG. 50 shows the backlight unit BLU used in this embodiment.

In this embodiment, the polarization splitting sheet 104 a, the liquidcrystal shutter 106, the polarization splitting sheet 104 b, and theprism sheet 112 are bonded in this order on the light guide plate 102,on the side of the liquid crystal panel A. The prism sheet 112 does nothave a reflection film on the prism surface 102 b.

Light propagating through the light guide plate 102 penetrates throughor is reflected by the polarization splitting sheets 104 a and 104 b andby the liquid crystal shutter 106 in the same mechanism as in theeighteenth embodiment. The light penetrated through the liquid crystalshutter 106 in the penetrative state is reflected by the prism surface102 b, and emitted toward the liquid crystal panel A.

In this embodiment, the same effect as by the eighteenth and twentiethembodiments can be obtained.

The Twenty-Second Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display deviceare the same as those of the twenty-first embodiment. In thisembodiment, elements corresponding to the elements described above forthe twenty-first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

FIG. 51 shows the backlight unit BLU used in this embodiment in detail.

In this embodiment, the retardation sheet 110 is pasted on the lightguide plate 102, on the opposite side of the liquid crystal panel A. Inthis embodiment, the same effect as by the nineteenth embodiment and thetwenty-first embodiment can be obtained.

The Twenty-Third Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display deviceare the same as those of the eighteenth embodiment. In this embodiment,elements corresponding to the elements described above for theeighteenth embodiment are given the same reference numerals andexplanation of these elements is not repeated.

FIG. 52 shows the backlight unit BLU used in this embodiment in detail.

In this embodiment, the polarization splitting sheet 104 a, the liquidcrystal shutter 106, the polarization splitting sheet 104 b are arrangedon the light guide plate 102 via an air layer 114, on the side of theliquid crystal panel A. A plurality of scattering patterns 116 areprinted in intervals on the light guide plate 102, on the opposite sideof the liquid crystal panel A. The patterns 116 may be formed as stripepatterns or check patterns. A reflection plate 118 is arranged adjacentto the light guide plate 102, on the opposite side of the liquid crystalpanel A.

A component of light penetrating through the light guide plate 102(unpolarized light) exceeding the critical angle due to the patterns 116is emitted on the polarization splitting sheet 104 a from the lightguide plate via the air layer 114[FIG. 52( a)]. Out of the unpolarizedlight, the abnormal light component is reflected by the polarizationsplitting sheet 104 b and returned to the light guide plate 102 via theair layer 114 [FIG. 52( b)]. The normal light component penetratesthrough the polarization splitting sheet 104 a and reaches the liquidcrystal shutter 106. In the case where the liquid crystal shutter 106 isin the state of birefringence (stippled portions in FIG. 52), the normallight component having penetrated through the polarization splittingsheet 104 a is subjected to the 900 phase shift by the liquid crystalshutter 106, and reflected by the polarization splitting sheet 104 b tobe returned to the light guide plate 102 [FIG. 52( c)]. On the otherhand, in the case where the liquid crystal shutter 106 is not in thebirefringence state (a white portion in FIG. 52), the light havingpenetrated through the polarization splitting sheet 104 a (the normallight component) penetrates through the liquid crystal shutter 106 andthe polarization splitting sheet 104 b, to be emitted toward the liquidcrystal panel A [FIG. 52( d)].

In this embodiment, the same effect as by the eighteenth embodiment canbe obtained. Furthermore, in this embodiment, the light penetratingthrough the light guide plate 102 easily exceeds the critical angle bythe scattering patterns 116, and the light is used efficiently.

The Twenty-Fourth Embodiment of the Liquid Crystal Display Device

Configurations of a main portion of the liquid crystal display deviceare the same as those in the twenty-third embodiment. In thisembodiment, elements corresponding to the elements described above forthe twenty-third embodiment are given the same reference numerals andexplanation of these elements is not repeated.

FIG. 53 shows the backlight BLU used in this embodiment in detail.

In this embodiment, a polarization splitting sheet 120 is used insteadof the polarization splitting sheet 104 a. The polarization splittingsheet 120 lets the normal light component penetrate through andirregularly reflects the abnormal light component. As the polarizationsplitting sheet 120, “DRPF (Diffuse Reflective Polarizing Film)manufactured by Minnesota Mining and Manufacturing Company is used, forexample.

Out of light emitted from the light guide plate 102 to the polarizationsplitting sheet 120 via the air layer 114, the abnormal light componentis irregularly reflected by the polarization splitting sheet 120 andreturned to the light guide plate 120. Operations other than this arethe same as in the twenty-third embodiment.

In this embodiment, the same effect as by the twenty-third embodimentcan be obtained.

The polarization splitting sheets 104 a and 104 b used in the eighteenthto twenty-fourth embodiments are not limited to “Transmax”. Thepolarization splitting sheets may be formed with a plurality of filmshaving different refractive indices. Alternatively, the polarizationsplitting sheets may be formed with a prism array comprising a pluralityof prisms. As the polarization splitting sheets having a plurality offilms stacked, “D-BEF” manufactured by Minnesota Mining andManufacturing Company can be used. As the prism array, “Weber” ofMinnesota Mining and Manufacturing Company can be used.

The Twenty-Fifth Embodiment of the Liquid Crystal Display Device

FIG. 54 shows the TFT (Thin Film Transistor) driving liquid crystaldisplay device used in this embodiment.

In this embodiment, elements corresponding to the elements describedabove for the first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

The liquid crystal display device comprises the liquid crystal panel Ahaving TFTs and liquid crystal cells C laid out in the form of a matrix.The size of the liquid crystal cells C is approximately 100 μm×300 μm.The gate electrodes of the TFTs as switching elements are connected tothe scanning lines G1, G2, . . . , Gn. The drain electrodes of the TFTsare connected to the signal lines D1, D2, . . . , Dm. The sourceelectrodes of the TFTs are connected to display electrodes 122 of theliquid crystal cells C which will be explained later. Second pixelelectrodes 124 are formed along the scanning lines beneath the displayelectrodes 122. The width of the second pixel electrodes 124 isapproximately 10 μm. In this embodiment, a liquid crystal mode of theliquid crystal panel A is normally black in which light penetratesthrough when an electric field exists. The liquid crystal panel A adoptsliquid crystals having a fast response speed, such as the VA (VerticalAlignment) type or the OCB (Optically Compensated Birefringence) type.The liquid crystal panel A may adopt the TN (Twist Nematic) type.

FIG. 55 shows a cross section of the liquid crystal cell C along thesignal line Dm in FIG. 54.

The liquid crystal cell C is formed by sandwiching a liquid crystallayer 130 between a CF substrate 126 and a TFT substrate 128. Firstpixel electrode 132 is formed on the inner side of the CF substrate 126,and the display electrode 122 is formed on the inner side of the TFTsubstrate 128. The first pixel electrode 132 is connected to a groundline. The second pixel electrode 124 is formed on the inner side of theTFT substrate 128. The second pixel electrode 124 is connected to aground line.

A thin film 134 made of amorphous silicon having 0.4 μm thickness and 10μm width is formed between the second pixel electrode 124 and thedisplay electrode 122, by using a CVD technique. The resistibility ofthe amorphous silicon is 1E8–1E9 Ω cm, which is lower than theresistibility of the liquid crystal layer (1E14 Ωcm). The dielectricconstant of the amorphous silicon and the liquid crystal layer 130 are 5and “12”, respectively. The liquid crystal film 134 forms a subsidiarycapacitance.

FIG. 56 shows an equivalent circuit of the liquid crystal cell C shownin FIG. 55.

The liquid crystal cell C can be dealt with as two CR time constantcircuits in which a capacitance CLC of the liquid crystal layer 130,resistance RLC thereof and a capacitance CS of the subsidiarycapacitance, resistance RS thereof are connected in parallel. Atransient phenomenon of the equivalent circuit is expressed by thefollowing Equations (4)˜(6), with t being time and V being a voltage:V(t)=V 0×exp(−t/CR)  (4)C=CLC+CS  (5)R=(RLC×RS)/(RLC+RS)  (6)

FIG. 57 shows a state in which display data (white) are written in theliquid crystal cells C.

The scanning line Gn is selected and the data are written in the liquidcrystal cells C. A voltage between the first pixel electrode 132 and thedisplay electrode 122 reaches a predetermined value, and penetrabilityof the liquid crystal layer 130 increases. Since the voltage between thetwo electrodes decreases according to equation (4), the penetrability ofthe layer 130 decreases. Therefore, the liquid crystal cell Cs areautomatically reset after the display data are displayed. In otherwords, black data are displayed. As a result, the impulse driving inwhich the display data and the reset data are written in one frameperiod (16.6 ms) can be realized. By writing the display data with avoltage equal to or larger than a saturation voltage, the transmissivitycan be increased.

Issues of discussion in the present invention will be described below.

FIG. 58 shows a change in the voltage supplied to the equivalent circuitshown in FIG. 55 in relation to the CR time constant. In order todisplay black data in the latter half of one frame period, it ispreferable for the supplied voltage to become equal to or less than 20%of an initial voltage in 16.7 ms. At this time, the CR time constantbecomes 0.01 or smaller.

FIG. 59 shows a change in the supplied voltage in the case of formingthe CR time constant circuit by using amorphous silicon. The amorphoussilicon satisfies the condition explained by using FIG. 58.

FIG. 60 shows a change in the supplied voltage in the case of theamorphous silicon having a d [μm] thickness and an S [μm²] area. Whend/S<2000[1/μm], the condition explained for the case of FIG. 58 issatisfied. As a result, the impulse driving can be carried out even ifthe width of the amorphous silicon is 3 μm (a minimum pattern in amanufacturing process). The smaller the area S of the amorphous silicon(the subsidiary capacitance) is, the larger the aperture ratio of theliquid crystal cells C becomes. Therefore, the high-brightness liquidcrystal panel A can be formed. The area of the subsidiary capacitance ispreferably equal to or less than 10% of the area of the displayelectrode 122.

FIG. 61 shows a change in the supplied voltage in relation to a changein thickness of the amorphous silicon. Generally, in a semiconductormanufacturing process, an approximately ±5% change in a layer thicknessneeds to be considered. Meanwhile, if the thickness change exceeds ±5%,unevenness may occur in the brightness of the liquid crystal panel A. InFIG. 61, an error in the CR time constant against the thickness changeof ±5% is not observed when d/S<400[1/μm]. In other words, ifd/S<400[1/μm], unevenness in the brightness of the liquid crystal panelA does not easily occur.

As has been described above, the liquid crystal display device in thepresent invention can carry out the impulse driving of the liquidcrystal panel A by using a charge/discharge characteristic of the liquidcrystal cells C, without using a special control circuit. As a result,blurring in a moving image can be alleviated and flicker is prevented.

In the above embodiment, the subsidiary capacitance is formed withamorphous silicon. However, the present invention is not limited to thisexample, and the subsidiary capacitance may be formed with a compositematerial of silicon nitride and carbonate silicon. At this time, thesubsidiary capacitance may be formed by using a CVD method, using amixture gas of silicon nitride and silicon carbonate. Alternatively, twolayers formed with silicon nitride and silicon carbonate may be used.Furthermore, the subsidiary capacitance may be formed by placing asilicon nitride layer and a silicon carbonate layer adjacent to eachother.

Furthermore, the liquid crystal display device may comprise a brightnesscorrection circuit for adjusting a difference of brightness in theliquid crystal cells C in relation to a change in the layer thickness.In this case, uneven brightness is not observed if the layer thicknesschanges by more than ±5%.

The Twenty-Sixth Embodiment of the Liquid Crystal Display Device

FIG. 62 shows in detail the penal A used in this embodiment.Configurations of a main portion of this device are almost the same asthose shown in FIG. 54.

In this embodiment, elements corresponding to the elements describedabove for the twenty-fifth embodiment are given the same referencenumerals and explanation of these elements is not repeated.

The liquid crystal panel A comprises the liquid crystal cells C laid outin the form of a matrix. The pixel electrode in each of the liquidcrystal cells C is connected to source electrodes of two TFTs 136 and138. A threshold voltage of the TFT 138 is set higher than that of theTFT 136. Drain electrodes of the TFTs 136 are connected to the signallines. Drain electrodes of the TFTs 138 are connected to electrodes 140to which a voltage corresponding to the reset data (black data) issupplied. The electrodes 140 are formed along the signal lines. Gateelectrodes of the TFTs 138 are connected to a scanning line Gn+1 (ascanning line scanned after Gn) which is adjacent to the scanning lineGn controlling the TFTs 136 of the liquid crystal cells C to which theTFTs 138 are connected. In other words, the gate electrodes of the TFTs136 and 138 connected to the liquid crystal cells C (pixel electrodes)adjacent to each other in the direction the scanning lines are connectedto the same scanning line Gn. Since the number of the scanning lines isthe same as in a conventional device, a penetrative efficiency of theliquid crystal panel A is prevented from decreasing.

In this embodiment, the mode of the liquid crystal panel A is normallyblack meaning that light penetrates through the liquid crystal panelwhen an electric field exists. The liquid crystal panel A may adoptliquid crystals having a fast response time, such as the VA (VerticalAlignment) type or the OCB (Optically Compensated Birefringence) type.The liquid crystal panel A may adopt a ferroelectric type, ananti-ferroelectric type, or the TN (Twisted Nematic) type.

FIG. 63 shows a structure of the TFT 136. The TFT 138 has an almost thesame structure.

The TFT 1.36 is formed by arranging a gate electrode 136 b and asemiconductor layer 136 c facing each other via a gate insulator 136 aand by connecting a data electrode 136 d (drain electrode) and a pixelelectrode 136 e (source electrode) to the semiconductor layer 136 c.

The threshold voltages of the TFTs 136 and 138 are adjusted by changingthe thickness of he gate insulator 136 a. More specifically, the TFT 138has the insulator layer thicker than the TFT 136. Like a general MOSFET,the threshold value can be adjusted by:

-   (1) changing the material of the gate insulator 136 a-   (2) changing the material of the semiconductor layer 136 c-   (3) changing an impurity concentration of the semiconductor layer    136 c.

FIG. 64 shows an operation of the liquid crystal panel A.

In this embodiment, each of the scanning lines is scanned twice in oneframe period (16.7 ms), and a line-sequential operation is carried out.The scanning lines are selected at a second time at a voltage higherthan at a first time. More specifically, the voltage at which thescanning lines are selected at the first time is higher then thethreshold voltage of the TFTs 136 and lower than that of the TFTs 138.The voltage at which the scanning lines are selected at a second time ishigher than the threshold voltage of the TFT 138.

The scanning line Gn is selected first and display data are written inthe liquid crystal cells C (a hatched portion of a display screen shownin FIG. 64( a)). The voltage of the scanning line Gn is lower than thethreshold value of the TFT 138. Therefore, reset data are not written inthe liquid crystal cells C. Display screens shown in FIG. 64( a)˜(d)show only changes in the liquid crystal cells C corresponding to thescanning line Gn.

The scanning line Gn+1 is then selected and display data are written inthe liquid crystal cells C (a hatched portion of the display screen(b)).

5 ms after the selection of the scanning line Gn for the first time inone frame period, the second-time selection thereof (at the highervoltage) is carried out. At this time, the display data corresponding toanother line are written in the liquid crystal cells C corresponding tothe line Gn. At the same time, reset data (black data) are written inthe liquid crystal cells C corresponding to the scanning line Gn−1 (ahatched portion and a black portion of the display screen (c).

A high voltage is then supplied to the scanning line Gn+1 and displaydata corresponding to another scanning line are written in the liquidcrystal cells C corresponding to the line Gn+1. At the same time, thereset data (black data) are written in the liquid crystal cells Ccorresponding to the line Gn (a hatched portion and a black portion inthe screen (d)). In other words, the invalid display data written in theliquid crystal cells C corresponding to the scanning line Gn in thescreen (c) are overwritten with the black data.

As has been described above, in this embodiment, the impulse driving inwhich the display data and the reset data are written alternately can becarried out, without increasing the number of the scanning lines andwithout causing the control circuit to become complex. In this manner,blurring in a moving image can be alleviated and flicker is prevented.

The Twenty-Seventh Embodiment of the Liquid Crystal Display Device

FIG. 65 shows the liquid crystal panel A used in this embodiment indetail. Configurations of a main portion of this device are the same asin FIG. 54.

In this embodiment, elements corresponding to the elements describedabove for the twenty-sixth embodiment are given the same referencenumerals and explanation of these elements is not repeated.

In this embodiment, the electrodes 140 to which the voltagecorresponding to the reset data (black data) is supplied are formedalong the scanning lines. Configurations other than this are the same asthose in the twenty-sixth embodiment.

In this embodiment, the same effect as by the twenty-sixth embodimentcan be obtained.

The Fourteenth Embodiment of the Liquid Crystal Display DeviceControlling Method

FIG. 66 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment.

In this embodiment, elements corresponding to the elements describedabove for the first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

The liquid crystal display device has the liquid crystal panel Acomprising the TFTs and the liquid crystal cells C laid out in the formof a matrix. The scanning lines G1, G2, Gn are signal lines fortransmitting gate signals output from the Y driver (gate driver) 14. Thesignal lines D1, D2, . . . , Dm are signal lines for transmitting datasignals output from the X driver (data driver) 16. The X driver 14 andthe Y driver 16 are controlled by the control circuit 18. The controlcircuit 18 receives display data and a clock signal from the exterior.The control circuit 18 outputs to the Y driver 14 a scan starting signalGSTR, a clock signal GCLK, a gate signal controlling signal DTGOE forwriting display data, and a gate signal controlling signal BLGOE forwriting reset data (black data). The control circuit 18 outputs to the Xdriver 16 display data DISP for one line, and a driver outputcontrolling signal LP for controlling an output timing of the displaydata.

FIG. 67 shows the control circuit 18 in detail.

The control circuit 18 comprises data receiving unit 18 a, a data drivercontrol unit 18 b, a gate driver control unit 18 c, a gate scanning linejudgment unit 18 d, a GOE generating unit 18 e, a gate scanningcondition memory unit 18 f, a blanking period judgment unit 18 g, and ablanking period memory unit 18 h.

The data accepting unit 18 a accepts the display data and the clocksignal and outputs the accepted signals to the data driver control unit18 b and to the gate driver control unit 18 c. The data driver controlunit 18 b generates the display data DISP and the driver outputcontrolling signal LP. The gate driver control unit 18 c receives thegate signal controlling signal DTGOE generated by the GOE generatingunit 18 e and a timing signal which the gate signal controlling signalBLGOE is based on. The gate driver control unit 18 c outputs the gatesignal controlling signal DTGOE and the gate signal controlling signalBLGOE. The gate scanning line judgment unit 18 d detects a fact that ½ aframe has been scanned after a start of display data writing and causesthe gate driver control unit 18 c to output the gate signal controllingsignal BLGOE for writing the black data.

The gate scanning condition memory unit 18 f stores a scanning conditionof the gate signals in an immediately proceeding frame. The blankingperiod judgment unit 18 g counts how many times the gate signals can bescanned within a blanking period which is a period between scan of thelast scanning line in which the display data are written and an end ofone frame. The blanking period memory unit 18 h stores the value countedby the blanking period judgment unit 18 g.

After the scan of the last scanning line to write the display data, thegate driver control unit 18 c and the data driver control unit 18 boperate under control of the blanking period judgment unit 18 g so thatthe black data are written a number of times according to the valuestored in the blanking period memory unit 18 h. Display of the liquidcrystal panel A will be explained in detail with reference to FIG. 69.

FIG. 68 shows an operation of the control circuit 18.

At the start of one horizontal scan period, the driver outputcontrolling signal LP is output once. At the fall of the driver outputcontrolling signal LP, display data DOUT are latched, and output for aperiod of the driver output controlling signal LP being low level.During a period in which the driver output controlling signal LP is highlevel, the black data DOUT are output. The voltage of the black data isset to be a central voltage (VDD/2) of an AC power source generating thedisplay data.

The gate signal controlling signal DTGOE becomes low level while thedriver output controlling signal LP is low level. The gate signalcontrolling signal BLGOE becomes low level during the time the driveroutput controlling signal LP is high level. A gate signal Gn(BL) forwriting the black data is generated when a basic gate signal GOUTgenerated within the control circuit 18 is high level and the gatesignal controlling signal BLGOE is low level at the same time. Likewise,the basic gate signal GOUT being high level and the gate signalcontrolling signal DTGOE being low level generate a gate signal Gn(DT)for writing the display data. In synchronization with the gate signalGn(BL), the black data (DOUT) are written. The display data (DOUT) arewritten in synchronization with the gate signal Gn(DT) for writing. Inother words, the control circuit 18 in this embodiment can output notonly the display data but also the black data (2 values) in the onehorizontal period.

FIG. 69 shows an operation of the liquid crystal panel A.

The scanning lines are sequentially scanned in one frame period anddisplay data are written. A ½ frame after the display data writing, thescanning lines are sequentially scanned again and the black data (B) arewritten. In other words, impulse driving is carried out. The black dataare written by using the data DOUT output when the driver outputcontrolling signal LP is high level, as has been described above.

The control circuit 18 sequentially scans the scanning lines in theblanking period and performs the black data writing control. Therefore,a display data retaining period T1 in which the display data aredisplayed is constant at all times.

Pulses shown by dashed lines are timings at which the black data areconventionally written. In this case, the display data retaining periodT1 is different between an upper area and a lower area of the liquidcrystal panel A.

FIG. 70( a) shows an outline of the display of the liquid crystaldisplay device to which the present invention has been applied. Displayperiods of the display data and the black data are always constant.

FIG. 70( b) shows an outline of the display of a conventional device.The display periods of the display data and the black data aredifferent, marking a border at the center of the screen. Therefore,brightness becomes different in the lower and the upper areas of thescreen, which means uneven display.

AS has been described above, in the controlling method of the presentinvention, impulse driving is carried out in such a manner that the twovalues of the display data and the black data are output in the onehorizontal period. Therefore, blurring in a moving image can bealleviated and flicker is prevented.

The black data are sequentially written in the blanking period.Therefore, brightness of the display data in the liquid crystal panel Acan be uniform and uneven display is prevented from occurring.

Furthermore, a conventional data driver for generating the display datacan be used as it is for carrying out the impulse driving.

The Fifteenth Embodiment of the Liquid Crystal Display DeviceControlling Method

FIG. 71 shows an operation of the control circuit 18. Configurations ofa main portion of the liquid crystal display device are the same as inFIG. 66.

In this embodiment, elements corresponding to the elements describedabove for FIG. 66 are given the same reference numerals and explanationof these elements is not repeated.

The control circuit 18 shifts the voltage of the black data from thecentral voltage (VDD/2) of the AC power source generating the displaydata to positive side or to negative side by VBL+ and VBL−,respectively. More specifically, the voltage of the black data isshifted to VBL+ and VBL− when a polarity selection signal POL is highlevel and low level, respectively. Operations other than this are thesame as in FIG. 68.

In this embodiment, the same effect as by the fourteenth embodiment ofthe controlling method can be obtained. Furthermore, in this embodiment,the alternating current driving is carried out for the black data, whichleads to secure display of the black data.

The Sixteenth Embodiment of the Liquid Crystal Display DeviceControlling Method

FIG. 72 shows an operation of the control circuit 18. Configurations ofa main portion of the liquid crystal display device are the same as inFIG. 66.

In this embodiment, elements corresponding to the elements describedabove for FIG. 66 are given the same reference numerals and explanationof these elements is not repeated.

The control circuit 18 shortens an output period of the display data byshortening a low-level period of the driver output controlling signalLP. Since a high-level period of the driver output control signal LPbecomes relatively longer, an output period of the black data becomeslonger. Active periods of the gate signals Gn(DT) and Gn(BL) are thesame. In this embodiment, the width of a gate pulse for writing theblack data can be substantially long and the black data are written withcertainty.

Since the display data output period becomes shorter, the display areafor the display data are divided into two, one area in the right and theother area in the left. For each area, the scanning lines are scannedand the display data are displayed.

The Seventeenth Embodiment of the Liquid Crystal Display DeviceControlling Method

FIG. 73 shows an operation of the liquid crystal panel A. Configurationsof a main portion of the liquid crystal display device are the same asin FIG. 66.

The control circuit 18 writes the black data a plurality of times in oneframe period. In other words, black data writing is complemented.Therefore, the black data can be written with certainty.

In the fourteenth embodiment of the controlling method described above,the gate signal Gn(DT) for writing the display data is generated byusing the basic gate signal GOUT and the gate signal controlling signalDTGOE. However, the present invention is not limited to this example,and the control may be simplified. The basic gate signal GOUT may besimply used as the gate signal Gn(DT), for example. In this case, thedisplay data are written over the black data having been written in thepixel electrodes. This causes no problem on display quality.

In the sixteenth embodiment of the controlling method described above,the active periods of the gate signal Gn(DT) and the gate signal Gn(BL)are the same. However, the present invention is not limited to thisexample, and a ratio of the active period of the gate signal Gn(DT) tothe active period of the gate signal Gn(BL) can be set arbitrarily.

The Twenty-Eighth Embodiment of the Liquid Crystal Display Device

FIG. 74 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment.

In this embodiment, elements corresponding to the elements describedabove for the first embodiment are given the same reference numerals andexplanation of these elements is not repeated.

The liquid crystal display device comprises the liquid crystal panel Ahaving TFTs (not shown) and liquid crystal cells C laid out in the formof a matrix. The liquid crystal panel A is controlled by the X driver 16and the Y driver 14. A backlight 141 is arranged on the backside of theliquid crystal panel A. The backlight 141 is formed with 10 cold cathodetubes (luminescent parts) laid out in parallel along the scanning lines.The X driver 16, the Y driver 14, and the backlight 141 are controlledby a control circuit 142. The driving frequency in this case is 60 Hz.

In this embodiment, the liquid crystal panel A adopts a TN (TwistedNematic) type panel having a 2.2 μm liquid crystal layerthickness(15-inch panel, 1024×768 pixels). A dielectric constant ε, arefractive index n, an N−1 transition temperature, and a response timeτm of these liquid crystals are −3.2, 0.2007, 70° C., and 14 ms,respectively. By sequentially turning on and off the cold cathode tubesof the backlight 141, impulse driving is carried out. A duty ratio whichis a ratio of an on-state period of the light to one-frame period is10%.

FIG. 75 shows a ground for determining conditions (the response time ofthe liquid crystal, the number of the cold cathode tubes, and the dutyratio) adopted in this embodiment.

Generally, when a change in brightness due to a transient response ofthe liquid crystal cells C after the luminescent parts such as the coldcathode tubes are turned on exceeds 5% of the brightness during theperiod in which the luminescent parts are on (a stippled portion in FIG.75), it is said that ghosts appear in an image or blurring in the imagebecomes conspicuous. Therefore, if impulse driving, in which thescanning lines corresponding to the luminescent parts are scanned in theoff-period of the luminescent parts (off in FIG. 75) and writing displaydata is started, is carried out, the brightness change of the liquidcrystal cells C (a hatched area S in FIG. 75) occurring after theluminescent parts becomes on needs to be equal to or less than 5%.

FIG. 76 shows a reference for measuring the response time of the liquidcrystals.

Maximal and minimal brightness of the liquid crystals are set to 100 and0 respectively, and voltages causing the brightness to be 0, 25, 50, 75,and 100 are defined as V0, V25, V50, V75, and V100. A maximum of theresponse time of these five voltages is defined as the response time ofthe liquid crystals. The response time is obtained by measuring the riseand the fall. The response time is also defined as the time at which 95%of a predetermined transmission ratio is obtained.

FIG. 77 shows the conditions of the liquid crystal response time, thenumber of division of the luminescent parts (the number of the coldcathode tubes), and the duty ratio for not causing ghosts or blurring.FIG. 77 shows the case of one frame period being set to 16.7 ms. Bydividing the horizontal axis by a frame time T, FIG. 77 becomes a graphnot depending on time. In this case, even if one frame period T isdifferent from 16.7 ms, FIG. 76 is also valid for a ratio of T to τ m.

The conditions adopted in this embodiment are shown by FIG. 77( a).Problems such as ghosts occur when the adopted conditions are arrangedin the lower right side of each curve. By using the conditions in thisembodiment, ghosts do not appear even if the number of the cold cathodetubes is 7. In the case where the duty ratio is set to 20%, ghostsappear. In the case where the liquid crystals having a 14 ms responsetime is used and the duty ratio is set to 20%, the number of the coldcathode tubes needs to be 14 or more.

Likewise, if the liquid crystals having an 11 ms response time are usedand the duty ratio is set to 40% or more, the number of the cold cathodetubes needs to be equal to or larger than 10 [FIG. 77( b)]. When liquidcrystals having an 8 ms response time are used and the duty ratio is 50%or more, the number of the cold cathode tubes is 7 or more [FIG. 77(c)]. In the case where an anti-ferroelectric liquid crystals ofthresholdless type having a 56 pC/cm² spontaneous polarization, a 1.5 μmlayer thickness, and a 0.55 ms response time are used and the duty ratiois set to 80%, the number of the cold cathode tubes needs to be 5 ormore [FIG. 77( d)]. When the duty ratio is large, it is advantageous forimproving the brightness.

As has been described above, in the liquid crystal display device inthis embodiment, the number of the cold cathode tubes, the ratio of theon-period of the cold cathode tubes to one frame period (the duty ratio)and the response time of the liquid crystal cells C are determined sothat the change in brightness due to the transient response of theliquid crystal cells C after turning on the cold cathode tubes becomesequal to or less than 5% of the brightness in the on-period of the coldcathode tubes. Therefore, ghosts and blurring in an image can beprevented.

The Twenty-Ninth Embodiment of the Liquid Crystal Display Device

FIG. 78 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device used in this embodiment.

In this embodiment, elements corresponding to the elements describedabove for the twenty-eighth embodiment are given the same referencenumerals and explanation of these elements is not repeated.

In this embodiment, a backlight system is formed with a liquid crystalshutter 144 and a backlight 146 which is always on. The liquid crystalshutter 144 has transparent electrodes made of ITO (Indium Tin Oxide)divided into 9 areas along the scanning lines. The transparentelectrodes form 9 areas 144 a. By causing one or a plurality of theareas 144 a to be in a penetrative state letting light from thebacklight 146 penetrate through, a plurality of luminescent parts whichwill be explained later are formed. The backlight 146 has a function ofemitting light including ultraviolet components. A phosphor covers aninner surface of the liquid crystal panel A, on the opposite side of theliquid crystal shutter 144. By the surface covered with the phosphor, aviewing angle of an image displayed on the liquid crystal panel Abecomes larger and display data can be displayed at high brightness.

FIG. 79 shows how the luminescent parts are formed.

In an odd-number frame, every two areas 144 a neighboring each otherpositioned up to the eighth area are in the penetrative state (becomeluminescent parts). The ninth area 144 a is in the penetrative state(luminescent part) by itself. Within one frame period, five luminescentparts are sequentially turned on and off.

In an even-number frame, the first area 144 a is in the penetrativestate (luminescent part) by itself. Every two neighboring areas 144 abetween the second area and the ninth area are in the light penetratingstate (luminescent parts). Within one frame period, these fiveluminescent parts are sequentially turned on and off. Positions of theboundaries of the luminescent parts are different between the odd-numberframes and the even-number frames. By carrying out the impulse drivingwhile moving the boundaries of the luminescent parts in every frame, theboundaries become inconspicuous.

In this embodiment, the OCB (Optically Compensated Birefringence) typeliquid crystal having 7 ms response time is adopted and impulse drivingis carried out by setting the duty ratio to 60%. These conditionssatisfy FIG. 77 and no ghosts appear.

In this embodiment, the same effect as by the twenty-eighth embodimentcan be obtained. Furthermore, in this embodiment, the luminescent partareas turned on at the same time change in every frame. Therefore, theboundaries become inconspicuous.

In the twenty-eighth embodiment described above, the liquid crystalpanel A adopts the TN (Twisted Nematic) type panel. However, the presentinvention is not limited to this example, and the ferroelectric type, orliquid crystals having a fast response speed may be adopted for theliquid crystal panel A.

The Thirtieth Embodiment of the Liquid Crystal Display Device

FIG. 80 shows an outline of the TFT (Thin Film Transistor) drivingliquid crystal display device.

In this embodiment, elements corresponding to the elements describedabove for the twenty-eighth embodiment are given the same referencenumerals and explanation of these elements is not repeated.

The liquid crystal display device comprises a control circuit 148 and aninterpolating circuit 150 for carrying out motion compensation. Theinterpolating circuit 150 receives display data supplied from theexterior and carries out motion compensation to output estimate data tothe control circuit 148. The liquid crystal panel A adopts a 15-inch VA(Vertical Alignment) type panel. The number of the pixels in the liquidcrystal panel A is 1024×768. The dielectric constant E and therefractive index n of the liquid crystals are −3.8 and 0.0082,respectively. The backlight 146 is formed by cold cathode tubesrepeatedly turning on and off at a 50% duty ratio. One frame period is16.7 ms (60 Hz).

FIG. 81 shows an outline of an operation and motion compensation of theliquid crystal display device.

In this embodiment, the scanning lines Gn (768 lines) are sequentiallyscanned. The backlight 146 is turned on in the first half of one frameperiod and turned off in the latter half. In this manner, impulsedriving is carried out. The backlight 146 is turned off at the time thescanning lines G384˜G768 are scanned. The display data written in theliquid crystal cells C corresponding to the scanning lines G384–G768 areoutputted to the exterior when the backlight 146 is turned on in asubsequent frame. The display data written in the scan of the scanninglines G289–G383 are outputted to the exterior in a short period duringthe backlight 146 is on in the current frame.

Therefore, in this embodiment, motion compensation is carried out on thedisplay data written in the scanning lines G289˜G768. Practically, theestimate data to be displayed at a start of the subsequent frame shownby a hatched area in FIG. 81 are written at the scan of the scanninglines G289˜G768. The estimate data are calculated by interpolation usingthe display data in the frame and in the subsequent frame. The displaydata corresponding to the scan of the scanning lines G1˜G288 are writtenas they are, without being interpolated.

FIG. 82 shows the interpolating circuit 150 in detail.

The interpolating circuit 150 comprises a block division processing unit150 a, a matching block detecting unit 150 b, a frame memory 150 c, amotion vector calculating unit 150 d, a data interpolation unit 150 e,and a data composing unit 150 f.

The block division processing unit 150 a receives data of the currentframe corresponding to the scanning lines G289˜G768 and divides theliquid crystal panel A into 16×16 pixel regions. Motion compensation iscarried out in each region.

The matching block detecting unit 150 b compares the display data in thecurrent frame and in the preceding frame in every region and detects towhich region a predetermined region in the preceding frame has moved inthe current frame.

The frame memory 150 c stores display data for one frame.

The motion vector calculating unit 150 d calculates the motion vectorfor each region by using a technique generally called block matching.

The data interpolation unit 150 e carries out interior division of themotion vector in a predetermined ratio for each of the scanning lines Gnand finds the estimate data. The ratio of the interior division isdetermined according to time between the scan of the scanning line Gnand the backlight's becoming on in the subsequent frame.

The data composing unit 150 f composes the estimate data correspondingto the scanning lines G289˜G768 and the display data corresponding tothe scanning lines G1˜G288, and outputs the composed data as frame datato be displayed.

As shown in FIG. 81, the estimate data to be displayed in the subsequentframe shown by the hatched area are written at the scan of the scanninglines G289˜G768. As a result, blurring or awkward motion in a movingimage can be prevented. In other words, moving image quality isimproved.

In the thirtieth embodiment described above, the VA (Vertical Alignment)type panel is adopted for the liquid crystal panel A. However, thepresent invention is not limited to the above example, and an OCB(Optically Compensated Birefringence) type, a ferroelectric type, or ananti-ferroelectric type may be used, for example.

In the thirtieth embodiment described above, impulse driving is carriedout by turning on and off the backlight 146. However, the presentinvention is not limited to this example, and impulse driving may becarried out by controlling a backlight system comprising a backlight anda liquid crystal shutter. In this case, it is preferable for the liquidcrystals used for the liquid crystal shutter to be of a VA (VerticalAlignment) type, or an OCB (Optically Compensated Birefringence) type,or a ferroelectric type, or an anti-ferroelectric type.

In the thirtieth embodiment described above, the backlight 146 is turnedon and off at the 50% duty ratio. The smaller the duty ratio is, thedarker the screen becomes. In order to improve moving image quality, thebacklight 146 is preferably turned on and off at the 50% duty ratio orless.

The invention is not limited to the above embodiments and variousmodifications may be made without departing from the spirit and scope ofthe invention. Any improvement may be made in part or all of thecomponents.

1. A liquid crystal display device, comprising: a liquid crystal panelin which a plurality of signal lines for transmitting display pixel dataand a plurality of scanning lines for transmitting control signals arelaid out vertically and horizontally, and pixel electrodes are arrangedat intersections of the signal lines and the scanning lines viaswitching elements, wherein the device has a hold control function inwhich an image to be displayed is output in one entire frame period, andan impulse control function in which an image to be displayed is outputin a predetermined period within the one frame period and is not outputduring a remaining period within the one frame period, wherein said holdcontrol is carried out when said display image is shown with all of thepixel electrodes and is a still image, wherein said impulse control iscarried out when said display image is shown with all of the pixelelectrodes and is a moving image, wherein motion compensation is carriedout by using DCT (Discrete Cosine Transform), and wherein said displayimage is judged to be said moving image and said hold control isswitched to said impulse control when compressed image informationincludes vector information indicating image motion.